On Tuesday, 43 people were killed at a UN-run school in the northern town of Jabaliya after Israeli forces fired tank shells at the building where families fleing the fighting had sought shelter. Two other schools were hit, killing a further five people. "Staff members have been killed, our installations have been hit, our refugees have been killed. All this in spite of the fact we have coordinated in detail the GPS coordinates of our installations and movement of vehicles and personnel with Israel," Gunness told AFP.

He has also told reporters that a three-hour pause in fighting by Israeli forces is insufficient, adding that the "humanitarian crisis is deepening with each hour." Israel insists it is doing its utmost to protect civilians and aid workers in its operations against Hamas, Gaza's Islamist rulers who have been firing daily volleys of rockets at the Jewish state. But aid agencies complain relief workers and medics are at high risk and that civilians have nowhere to flee.

"The parties must respect the norms of international humanitarian law, in particular the principles of distinction and proportionality," said UN humanitarian coordinator for the Palestinian territories, Maxwell Gaylard. The International Committee of the Red Cross (ICRC) on Thursday accused Israel of failing to help wounded people in an area of Gaza where its rescuers found four small children huddling next to their dead mothers, too weak to stand up.

It said Israeli soldiers tried to force the rescuers to leave when they finally reached the grisly scene in Gaza City's shell-battered Zeitun neighbourhood on Wednesday, four days after safe-passage had been requested. The delay in allowing access to rescuers was "unacceptable," the ICRC said. "This is a shocking incident," said Pierre Wettach, who heads the ICRC's delegation for Israel and the Palestinian territories. "The Israeli military must have been aware of the situation but did not assist the wounded."

The rescuers evacuated 18 wounded and 12 others "who were extremely exhausted," the ICRC said, adding that more wounded people are sheltering in destroyed houses. In a statement issued in Geneva ICRC president Jakob Kellenberger said: "It must be possible to evacuate wounded at all times, not just during three hours."

The Israeli military said it would investigate the claims if a complaint is received but insisted it works "in close cooperation with international aid organisations during the fighting so that civilians can be provided with assistance." It also stressed Israeli troops were involved in fighting "the Hamas terrorist organization who have deliberately used Palestinian civilians as human shields." Amnesty International has accused both Israeli soldiers and Palestinian fighters of using civilians as "human shields."

It claimed Israeli soldiers took up up positions in Palestinian homes, "forcing families to stay in a ground floor room while they use the rest of their house as a military base and sniper position." Asked about the claim, an Israeli military spokesman said "the IDF does not comment on ongoing operations."

A total of 763 Palestinians have been killed in Gaza since Israel launched Operation Cast Lead on December 27. AFP