Israeli aircraft on Sunday killed two Palestinians, one a 12-year-old boy, medical sources in Gaza said, as cross border violence continued for a third day with militants firing rockets into the Jewish state.

Medics said the boy was killed by an Israeli air strike in the northern Gaza Strip and identified him as Ayoub Assaleya. A Palestinian militant was killed in a separate strike in Gaza City, they said.

An Israeli military spokeswoman confirmed the strikes and said the army was checking on the reports that a boy was killed.

"Aircraft targeted a terrorist squad that was in the final stages of preparing to fire rockets at Israel from the northern Gaza Strip," a military statement said, adding that an additional strike targeted two rocket launching sites.         
Sunday's attacks brought to 17 the number of Palestinians killed since Friday, when Israeli missiles killed two militant leaders. Sixteen of those killed were Palestinian militants, Palestinian officials said.

Militant groups in Hamas-ruled Gaza vowed to exact revenge and have fired more than 100 rockets into southern Israel since Friday, injuring six people, one of them seriously. 

Six more projectiles were fired from Gaza on Sunday, an Israeli police spokesman said.

Islamic Jihad and the Popular Resistance Committees (PRC), an armed faction largely independent of Gaza's Islamist Hamas rulers, said it had fired most of the rockets and mortars. 

The escalating violence drew appeals for a ceasefire from the United Nations, the European Union, the West Bank-based Palestinian Authority and neighbouring Egypt, whose peace treaty with Israel has been tested by last year's toppling of Hosni Mubarak. 

A Palestinian official speaking on condition of anonymity said Egypt had begun mediating a ceasefire on Sunday. The Egyptian Foreign Ministry had no comment.

Israeli Vice Prime Minister Moshe Yaalon said: "In the latest rounds of violence the Egyptians have naturally served as mediators. We are not negotiating with Hamas ... but deliver a clear message, if you don't shoot, we don't shoot, if you do shoot, you will pay a price."     

Hamas seized control of Gaza from Palestinian President Mahmoud Abbas's Fatah movement in a bloody 2007 coup, two years after Israel pulled its forces out of the territory it had captured in a 1967 war. - Reuters