The Red Cross has accused the Israeli army of hindering its rescue teams after saying it found four children lying next to their dead mothers in the wreckage of a shell-battered Gaza City neighbourhoood.

In a scathing statement, the International Committee of the Red Cross (ICRC) accused the Israeli army of failing to meet its obligation under international humanitarian law to care for and evacuate the wounded.

The Red Cross said its rescue teams had been refused access to the Zeitun neighbourhood for four days.

The delay in allowing access to rescuers was "unacceptable," the ICRC said.

When the rescue team, which included members of the Palestinian Red Crescent Society, was allowed into the area, it found four small children next to their dead mothers in one of the houses, the Red Cross said.

The ICRC said the children were too weak to stand up on their own.

"One man was also found alive, too weak to stand up. In all there were at least 12 corpses lying on mattresses," the ICRC said.

Fifteen survivors, several of them wounded, were found in one house.

The ambulances could not get over earth walls piled up by Israeli army bulldozers to block enemy fighters, so donkey carts were brought in to evacuate the survivors.

"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. Neither did they make it possible for us or the Palestine Red Crescent to assist the wounded."

Israel says the team could not go in because of fighting in the area, and that it does coordinate with aid agencies.

But it is coming under increasing international pressure over the civilian situation in the territory.

The United Nations Relief and Works Agency (UNRWA) has suspended its work in Gaza after one of its aid convoys was shelled by Israeli forces.

"UNRWA decided to suspend all its operations in the Gaza Strip because of the increasing hostile actions against its premises and personnel," Adnan Abu Hasna, a Gaza-based UNRWA spokesman said.

Mr Hasna did not say how long the suspension would last.

"A convoy going towards Erez came under fire, according to the contractor," said the UNRWA's Chris Gunness.

"Two tank shells impacted near a forklift, and one person was killed," he said.

"The forklift trucks had been contracted to pick up UN goods," he said, adding that the convoy had been coordinated with the Israeli military.

The Israeli army said it was investigating.

About 250 foreigners have been evacuated from Gaza City to Israel, but hundreds are believed to be still in the territory.