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.