Ahead of a trip to the region to push for a truce, Ban Ki-moon said too many people had died and there had been too much civilian suffering.

His call came as Israeli ground forces and tanks moved deeper into urban areas and air strikes across the Gaza Strip continued for a 17th day.

Prime Minister Ehud Olmert said Palestinian militants will keep on feeling Israel's "iron fist" as long as Hamas fires rockets at Israel.

Both Hamas and Israel rejected last week's UN Security Council resolution calling for an immediate ceasefire.

Palestinian medical sources say 910 people have been killed in Gaza so far, of whom 292 were children and 75 were women. Israeli officials say 13 Israelis, including three civilians, have been killed.

Nearly 30 rockets or mortars were fired on Israel from Gaza on Monday. Casualty reports from Palestinian medics ranged from nine to 26 dead, while Israel said five of its soldiers had been injured, one of them seriously.

Israel is preventing international journalists from entering Gaza, making it impossible to independently confirm casualty figures.