UN Secretary-General Ban Ki-moon will travel to the Middle East on Saturday in a bid to end the fighting between Israel and Palestinians, alarmed at a serious escalation that includes a ground offensive by Israel, said a senior UN official.

Israel intensified its land offensive in Gaza with artillery, tanks and gunboats on Friday and warned it could "significantly widen" an operation Palestinian officials said was killing ever greater numbers of civilians.

"Israel has legitimate security concerns, and we condemn the indiscriminate rocket fire from Gaza into Israel that ended yesterday's temporary ceasefire. But we are alarmed by Israel's heavy response," UN political affairs chief Jeffrey Feltman told the UN Security Council on Friday.

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