Israeli mortar rounds blasted a United Nations-run school that had been converted into a refugee shelter for hundreds of Palestinians displaced by the ten-day war in Gaza, killing more than 40 people today.

It was one of three UN schools hit by Israeli ordnance today. The strike against the Fakhora school in the northern town of Jabaliya was the deadliest single attack of an already blood-soaked offensive.

Israeli army officials said that their forces had been targeted by Hamas mortar fire from within the school compound. They named two alleged Hamas militants among the fatalities, Imad Abu Askar and Hassan Abu Askar.

The Israeli army has instructions to attack any position used by Hamas for firing rockets, an Israeli military source told The Times.

The deaths came as the Islamists were pushed back from their usual launch grounds to the east and into the packed metropolis of Gaza City and the surrounding refugee camps.

They pile more pressure on the international community to come up with a swift but durable formula to halt the carnage that has left more than 640 Palestinians dead.

President Sarkozy of France, who is on a peace mission to the region, said that a deal to end Israel’s offensive in Gaza was not far away. Tony Blair, the international community’s envoy, said that a ceasefire could be reached within days but was contingent on finding a way to stop Hamas rearming. His hope that a truce could be struck was echoed by Gordon Brown, who said that the Middle East faced its “darkest moment yet”.

The increasing violence forced Barack Obama, the US President-elect, to break his silence on Gaza. He expressed his “deep concern” at the killing of civilians.

The Fakhora school had been sheltering refugees driven from their homes by heavy fighting.

Screaming relatives tried to revive victims who lay motionless in pools of blood on the pavement outside the school, as cars and ambulances rushed the casualties to Gaza’s already overwhelmed hospitals.

Palestinian medics said at least 42 bodies were pulled from the wreckage of the school that had been providing shelter for about 350 refugees. The UN said it had confirmed at least 30 people were dead and another 55 wounded.

John Ging, the Gaza director for the UN refugee agency, said that the building had been clearly marked with a UN flag and its precise co-ordinates given to the Israeli army to avoid just such a tragedy.

The UN has run a number of schools in the Gaza Strip since the first wave of Palestinian refugees arrived more than 50 years ago.

Today’s incident could prove a turning point in the operation. The death of 28 Lebanese civilians in an Israeli bombing in the village of Qana during the 2006 Lebanon war caused support for Israel evaporate and hastened an end to the conflict. But there were also fears that the strike could trigger renewed violence, with Ayman al-Zawahiri, Osama bin Laden’s deputy, calling on Muslims to attack Western and Israeli targets around the world.

Israeli army officials said that its forces had been attacked by mortar fire from within the compound, saying it was not the first time UN schools had been used as firing positions by the Islamists. “An initial inquiry by forces on the ground indicates that a number of mortar shells were apparently fired at troops from within the schools and the forces responded by firing a number of mortar shells into the area,” they said in a statement.

Chris Gunness, a spokesman for the UN Relief and Works Agency, called for a full investigation. “We want to see if there have been violations of international law,” he said.

Mr Ging said that the area had been the scene of a number of clashes between Israeli and Hamas forces, “so there’s an intense military and militant activity in that area”. But he said that his staff vetted Palestinians seeking shelter for militants.

In an earlier strike on another UN school in Beach Camp, on Gaza City’s Mediterranean coast, three cousins were killed. A third UN school was struck in Rafah in the south after Israeli tanks moved into the nearby city of Khan Younis. A building next to a UN health clinic was damaged during the Israelis’ relentless offensive to smash Hamas’s military capability before a ceasefire is forced upon them.

The mounting death toll intensified international pressure for a truce deal, with talk of observers force being deployed. “I’m convinced that there are solutions,” Mr Sarkozy said during a visit to Lebanon, after meeting Israeli and Palestinian leaders in the West Bank, which is held by Hamas’s secular rivals, Fatah.

“We are not far from that. What is needed is simply for one of the players to start, for things to go in the right direction.”

Mr Blair said that a key element to any truce would be for security measures to be implemented on Gaza’s border with Egypt, which has been used by Hamas as a resupply route. There are believed to be hundreds of smuggling tunnels under the border, although Israeli airstrikes are believed to have destroyed at least 40 large tunnels in the past week.

Diplomats are discussing a possible Turkish role in monitoring a ceasefire in Gaza. Talks at the UN are focusing on the creation of an international presence to oversee the ceasefire, reopen border crossings into Israel, and prevent arms smuggling from Egypt. Turkey, a Nato member and Muslim nation with good relations with Israel, is expected to contribute personnel along with European nations, diplomats said.

Despite continuing to fire rockets into southern Israel, Hamas officials from Syria were due to hold talks in Egypt about a possible truce to end the latest bout of fighting, in which seven Israeli soldiers have died and three civilians been killed by rockets.

Israel claims Hamas fired from school as death toll hits 640 – Times Online