Gaza crisis: UN claims Israel did not allow evacuation from shelter before strikes - as it happened

US secretary of state John Kerry, in Cairo, has been diligently working the phones trying to negotiate a Gaza ceasefire, Harf says, having spoken multiple times today with diplomats in Europe, Turkey, Israel, Egypt, Qatar and elsewhere.

Harf is asked whether the US condemns the attack on the UNRWA school. She says she has already said the US is very concerned.

"We are still looking into all the facts," Harf says. "Let's not jump to conclusions before we have all the facts."

State department spokesperson Marie Harf reiterates the Psaki statement on the attack on the UNRWA shelter.

"We are deeply saddened and concerned at the tragic incident at the UNRWA school and at the rising civilian death toll in Gaza," she says.

Matt Lee of the AP asks Harf about the Israeli argument that the facility would be a legitimate target if it's a place where weapons are kept or from which attacks are launched.

If a warning had been given by the Israeli military to evacuate the shelter, but it remained full, is it still a legitimate target? Lee asks.

I'm happy to check with our legal folks, Matt. I don't wan't to make a legal judgment from the podium," Harf says.

She's asked whether the US state department believes Israel is taking care to prevent civilian casualties.

We do but again as I said... we think they could take additional steps to prevent civilian casualties. We think that remains the case.

A spokeswoman for U.S. Secretary of State John Kerry said a deadly Gaza school incident on Thursday in which at least 15 people seeking shelter were killed "underscores the need" for a ceasefire and resolution of the conflict, Reuters reports:

"This ... underscores the need to end the violence and to achieve a sustainable ceasefire and enduring resolution of the crisis in Gaza as soon as possible," said Jen Psaki, a spokeswoman for Kerry, who is trying to secure a truce to curtail 17 days of fighting.

"We again urge all parties to redouble their efforts to protect civilians," she said.

A state department briefing with Marie Harf is scheduled to begin soon.

The Israeli military has put out a new statement about the strikes on the UNRWA shelter in Beit Hanoun today. The statement says rocket attacks were coming from the area and that the Israeli army "responded by targeting the source of the fire."

The IDF statement plants many variant explanations for the bloodshed at the school – including the assertion that Hamas stopped civilians from leaving the shelter, an assertion that contradicts UN statements and reporters' observations that Israeli fire had driven civilians from their homes to the shelter and that no place in Gaza is safe for civilians. The IDF statement says in part:

In recent days, Hamas has fired rockets from an area of Beit Hanoun where an UNRWA shelter is located. Last night, we told Red Cross to evacuate civilians from UNRWA's shelter in Beit Hanoun btw 10 am & 2 pm. UNRWA & Red Cross got the message. Hamas prevented civilians from evacuating the area during the window that we gave them. Today Hamas continued firing from Beit Hanoun. The IDF responded by targeting the source of the fire. Also today, several rockets launched from Gaza toward Israel fell short and hit Beit Hanoun.

The UN says the number of displaced Palestinians during Israel's current 'protective edge' operation is more than double the peak number during 'cast lead':

An Israeli military spokesman directly contradicts UNRWA spokesman Chris Gunness, who said the UN "tried to coordinate with the Israeli Army a window for civilians to leave" the facility at Beit Hanoun "and [a window] was never granted".

Not true, says the IDF's Peter Lerner. There was a four-hour window, he says:

Al Monitor's Laura Rozen seeks clarification:

Reuven Rivlin, the next president of Israel, is to be sworn in today in a ceremony at the Knesset.

Shimon Peres is reading a valedictory statement. You can watch it live here.

British foreign secretary Philip Hammond said at news conference in Cairo on Thursday that Hamas must agree to a humanitarian ceasefire without conditions, Reuters reports. Egypt has been trying to mediate a truce.

As our live blog coverage continues, here's a summary of where things stand:

At least 15 people were killed and many wounded when Israeli tank shells reportedly struck a compound housing a UN shelter hosting hundreds of displaced Gazans in Beit Hanoun in the north. It was the fourth time a UN facility had been hit in the fighting.

The Israeli military said "rockets launched from Gaza" landed in Beit Hanoun on Thursday afternoon.

The latest figures from the Palestinian health ministry said 771 people had died in Gaza and 4,750 had been injured, with at least 76 killed today. More than 140,000 Gazans are displaced, according to the UN.

Six members of the same family and an 18-month-old infant boy were killed when an Israeli airstrike hit the Jebaliya refugee camp in the early morning hours, according to Gaza police and health officials.

An airstrike on a home in the southern Gaza town of Abassan, near Khan Yunis in the south, killed five members of another family, the ministry said.

The Israeli military said that 13 rockets had been fired out of Gaza Thursday and hit Israeli territory and seven additional rockets were intercepted by the Iron Dome system.