Tensions in Gaza have escalated further after an Israeli bombardment destroyed a high-rise building used by foreign press, followed up by the targeting of the home of one of Hamas’s leaders.

Israel‘s airstrike on the 12-storey tower block – an hour after people were told to evacuate the building – came as fighting raged despite international calls for a ceasefire.

The al Jalaa Tower in Gaza City, which houses Al Jazeera and the Associated Press (AP) news agency, among others, was hit twice by an Israeli bombardment at about 1.15pm on Saturday.

There were no reports of fatalities and an adviser to Israeli Prime Minister Benjamin Netanyahu said he was “very satisfied” that no journalists were hurt.

A spokesperson for the Israeli Defence Forces said: “The building contained civilian media offices, which the Hamas terror organization hides behind and uses as human shields. The Hamas terror organisation deliberately places military targets at the heart of densely populated civilian areas in the Gaza Strip.”

For 15 years, the AP’s top-floor office and roof terrace were a prime location for covering Israel’s conflicts with Gaza’s Hamas rulers, including wars in 2009 and 2014.

The news agency’s camera offered 24-hour live shots as militants’ rockets arched toward Israel and Israeli airstrikes hammered the city and its surrounding area this week.

AP’s president and CEO Gary Pruitt condemned the strike “incredibly disturbing”, saying the media outlet was “shocked and horrified”.

“We narrowly avoided a terrible loss of life,” he said. “A dozen AP journalists and freelancers were inside the building and thankfully we were able to evacuate them in time.

“The world will know less about what is happening in Gaza because of what happened today.”

Mr Netanyahu has insisted that Israel is doing everything to avoid harming those not involved in the Hamas strikes against his country, including a rocket attack that killed one Israeli near Tel Aviv.

Earlier, on what was the sixth day in a row of hostilities, some 10 Palestinians from an extended family – including eight children – were killed by an Israeli strike in Gaza City.

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Israel’s military also targeted the home of Khalil al-Hayeh, a top leader of Gaza’s ruling militant Hamas group.

It said that al-Hayeh served as part of Hamas’s “terrorist infrastructure”, suggesting Israel was now going after the militant group’s top leadership. It is unknown if he survived the blast or not.

Later on Saturday, US President Joe Biden spoke to Mr Netanyahu and Palestinian President Mahmoud Abbas in separate phone calls and urged a de-escalation in tensions.

The UN Security Council is set to meet to discuss the crisis on Sunday, after US diplomat Hady Amr arrived in the region on Friday as part of Washington’s efforts to de-escalate the conflict.

Meanwhile, the UK Foreign Office said: “The ongoing violence across Israel and the Occupied Palestinian Territories is deeply concerning and must end. There is never any justification for targeting innocent civilians.

“Both sides need to de-escalate and offer hope to their peoples, which can only come through political dialogue.”

Its statement came after tens of thousands of Londoners marched in solidarity with Palestinians, heading through Hyde Park to the Israeli Embassy, while Labour’s shadow foreign secretary Lisa Nandy condemned the “completely unacceptable” airstrike on the Gaza media building.

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Saturday’s escalation in violence came at the start of the Nakba, or “catastrophe”, an annual day of Palestinian grief marking the displacement of hundreds of thousands of refugees at the time of Israel’s creation in 1948.

It comes after days of attacks between Israel and Hamas.

Since Monday evening, Hamas has fired hundreds of rockets towards Israel, which responded by attacking the Gaza Strip with tanks and air strikes.

The number of people killed has climbed to at least 145 people in Gaza, including 41 children and 23 women, according to Palestinian health officials, and nine – including two children and a soldier – on the Israeli side.

A grieving Palestinian father has said his children were killed “without any warning” after an Israeli bombardment struck a house in Gaza City.

Eight children aged 14 and under and two women were killed instantly when the three-storey building, located in the Shati refugee camp, was struck at around 1.30am on Saturday.

Mohammed Hadidi told reporters that his wife and five children had gone to celebrate the Eid al-Fitr holiday with her brother’s wife and three of their children.

“The Israelis hit the house without any eviction, without any warning, without any calls, without anything,” he said.

“All the people are in the neighbourhood. And they are peaceful in their houses. They are all children.”

He said the eight children killed were aged between five and 14-years-old, and were his sons and the sons of his brother-in-law.

Mr Hadidi said his five-month-old son, Omar, is the only known survivor, while 11-year-old Yahya is still missing.

He said Omar was protected by God “from the three floors”, adding: “He’s five months old and he is injured at al-Shifa hospital now. And the rest are gone.”

Israeli Prime Minister Benjamin Netanyahu has insisted that Israel is doing everything to avoid harming those not involved in the Hamas strikes against his country, including a rocket attack that killed one Israeli near Tel Aviv.

Another Israeli strike on Saturday toppled a media building in Gaza, but journalists were able to escape after the occupants were given an hour’s notice to evacuate.

But children’s toys and a Monopoly board game could be seen among the rubble inside the destroyed building in the refugee camp, along with plates of uneaten food from the holiday gathering.

Mr Hadidi continued: “There is no future. There is no future from the beginning.

“Those are children, they didn’t fire any rockets or hit any jeeps or do any bombings.

“They were wearing their Eid clothes and going to celebrate Eid. You hit them while they’re asleep? While being peaceful in their house? Call them and they will leave.”

Mr Hadidi described the attacks on Palestine, which have been met by retaliatory strikes by Gaza’s ruling militant Hamas group, as a “crime against humanity, an international crime”.

He added: “We can hear the airstrikes. Who knows who’s going to die. Maybe we get up and start walking and die. There is no security because of the Israelis and their supporters.

“I deliver a message to the free people of the world, who have some humanity, those are children.

“What have they done? This is not the first war for us. This is the fourth war. And this isn’t the first family to lose their children and not the last.”

But he said “this is God’s destiny and we accept it”, adding he counts the children who died as “martyrs”.

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The Israel-Palestinian hostilities are now in their sixth day and diplomatic efforts to stop the violence are intensifying, including a phone call between Mr Netanyahu and US President Joe Biden.

At least 139 people have now died in Gaza, including 39 children and 22 women, as the death toll rose overnight, according to Palestinian health officials.

Nine people – including two children and a soldier – have died on the Israeli side.

A tower block that is the base for international media in Gaza has been hit by an Israeli bombardment, causing it to collapse.

The strike – an hour after people were told to evacuate the building – came as fighting raged.

Earlier, 10 Palestinians from an extended family, including eight children, were killed by an Israeli strike in Gaza City, and one Israeli was killed in a rocket attack near Tel Aviv.

The Israeli Defence Forces (IDF) posted footage of “the scene in the neighbourhood in Ramat Gan after a rocket from Gaza struck the area”, saying they “will not let this terror go unanswered”.

In other developments:

• The UN’s High Commissioner for Human Rights Michelle Bachelet called for strict respect for international law and appealed to all sides to take steps to de-escalate, as Malaysia and Indonesia called on the UN Security Council to intervene and stop Israel’s strikes on Gaza

• Egypt pushed for both sides to pause military activities from midnight on Friday, with Cairo leaning on Hamas, while the US and others tried to reach an agreement with Israel – but an Egyptian source said Israel turned down an Egyptian proposal for a one-year truce that Gaza’s militant Hamas rulers had accepted

• Amid the fighting, Palestinians marked the start of the Nakba, or “catastrophe”, an annual day of Palestinian grief marking the displacement of hundreds of thousands of refugees at the time of Israel’s creation in 1948

• The UN Security Council is also set to meet on Sunday, after US diplomat Hady Amr arrived in the region on Friday as part of Washington’s efforts to de-escalate the conflict

• The number killed rose overnight: 139 people have now died in Gaza, including 39 children and 22 women, according to Palestinian health officials, and nine – including two children and a soldier – on the Israeli side

• United Arab Emirates carriers Etihad Airways and flydubai cancelled flights to Tel Aviv, joining American and European airlines

• Iran’s foreign minister cancelled a visit to Austria after the Austrian government flew the Israeli flag in Vienna in a show of solidarity

• In London, hundreds of people have gathered to march in solidarity with Palestinians, with former Labour leader Jeremy Corbyn among those expected to speak

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The al Jalaa Tower, which houses foreign media – Al Jazeera and the Associated Press news agency, among others – was hit twice by an Israeli bombardment at about 1.15pm.

There were no reports of fatalities.

AP’s correspondent in Gaza, Fares Akram, said earlier that the building was the only place in the city he felt safe, as it was known to the Israelis as a media base.

Overnight on Saturday, the IDF said incoming rocket fire from Gaza had forced Israeli civilians to head to shelters to protect themselves for the fifth morning in a row, with the cities of Beersheba and Ashdod among those struck.

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Israeli military forces said they carried out strikes on a Hamas military intelligence facility and a number of rocket launching sites in northern Gaza, an enclave controlled by the Islamist Palestinian group.

An Israeli air strike killed eight children and two women from an extended family – the highest number of fatalities in a single hit since the Israel-Gaza conflict reignited earlier this week.

The 10 died when an airstrike hit a three storey house in a refugee camp in Gaza City, AP said, and a surviving widower told reporters that his wife and five children, only one of whom is known to have survived, had gone there to celebrate the Eid al Fitr holiday with relatives.

Soon after, Hamas said it fired multiple rockets at southern Israel in response.

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A total of 15 Palestinians were killed by Israeli bombardment overnight, according to Palestinian medics on Saturday.

Palestinians militants fired about 200 rockets at Israeli cities, and Israel’s military said its aircraft struck apartments that belonged to Hamas militants as well as rocket launch sites.

Ms Bachelet warned the firing of large numbers of indiscriminate rockets by Palestinian armed groups into densely populated Israeli areas amounts to war crimes – and there were concerns some attacks by the Israeli Defence Forces that have targeted “civilian objects” do not meet the requirements to be considered as military objectives under humanitarian law.

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She said: “Over the past 10 days, the situation in the Occupied Palestinian Territory and Israel has deteriorated at an alarming rate.

“Rather than seeking to calm tensions, inflammatory rhetoric from leaders on all sides appears to be seeking to excite tensions rather than to calm them.

“I urge both sides to ensure strict respect for their obligations under international law. Israel, as the occupying power, also has a duty to ensure unimpeded access to humanitarian assistance to the Gaza strip. Those found to be responsible for violations must be held to account.”

The Nabka, which has fallen on Saturday, is one of the most sombre dates of protest in the Palestinian calendar. It marks the day after the creation of the state of Israel on 14 May 1948, a move that led to hundreds of thousands of Palestinians fleeing or being expelled from the country.

This year, Nakba Day is expected to be particularly tense, coming as Israelis and Palestinians engage in their worst clashes in years and with street unrest rising in mixed Jewish-Arab neighbourhoods across Israel stirring fears of a descent into civil war.

Anti-Israeli protests also erupted in the occupied West Bank on Friday, prompting Israeli forces to open fire, killing 11 people.

In addition, pro-Palestinian demonstrations took place at Israel’s borders with neighbouring Jordan and Lebanon, while three rockets were reportedly fired towards Israel from Syria.

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The Israel-Palestinian hostilities are now in their sixth day and diplomatic efforts to stop the bloodshed are intensifying.

The US embassy in Jerusalem said Hady Amr’s aim after he arrived in Israel was “to reinforce the need to work towards a sustainable calm”.

As well as Egypt, Qatar, Jordan and the United Nations are also important players.

“The talks have taken a real and serious path on Friday,” a Palestinian official was quoted by the Reuters news agency as saying.

“The mediators from Egypt, Qatar and the United Nations are stepping up their contacts with all sides in a bid to restore calm, but a deal hasn’t yet been reached.”

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Diplomats have already held a number of closed-door sessions since the bombardments by both sides began on Monday.

The violence was sparked by tensions in Jerusalem over efforts by Jewish settlers to evict a number of Palestinian families from their homes in an east Jerusalem neighbourhood, and by clashes between Israeli police and Palestinians at a revered mosque in the Old City.

On Friday night, online video showed young Jewish nationalists firing pistols as they traded volleys of stones with Palestinians in the disputed Sheikh Jarrah neighbourhood.

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Israel’s bombardment of the Gaza Strip continued into early Saturday, followed by a salvo of Hamas rockets towards Israel.

The exchanges came after the heaviest barrage of Israeli tank and artillery fire, combined with airstrikes, overnight into Friday that pummelled the Palestinian enclave.

The Israeli military said that they had been going after a network of tunnels used by Hamas. But the onslaught wreaked destruction in some towns, killed a family of six in their house and sent thousands fleeing their homes.

Houda Ouda said she and her extended family ran frantically into their home in the Gaza town of Beit Hanoun, seeking safety as the earth shook in the darkness.

“We even did not dare to look from the window to know what is being hit,” she said.

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The Israeli Defence Forces has said Hamas and Islamic Jihad, a fellow Palestinian militant group, have fired more than 2,000 rockets from Gaza towards Israel since the start of the hostilities – an unprecedented volume of strikes.

More than 400 rockets are said to have fallen short into Gaza, while many more were blasted out of the sky by Israeli air defence systems. However, some did impact.

Across central and southern Israel, from small towns bordering Gaza to metropolitan Tel Aviv and southern Beersheba, Israelis have adjusted to sirens wailing, radio and TV broadcast interruptions and the beeps on their mobile phones of red alerts that send them rushing for cover.

For its part, the Israeli military said they have hit some 1,000 targets in Gaza, including rocket launch sites, individual commanders and the tunnel network.