Gaza: Israel killed 18 Palestinians, nearly all of them Hamas militants, in the Gaza Strip on Tuesday, in a raid the Palestinian Authority said was a "slap in the face" to US President George W. Bush's peace efforts.

The violence resulted in the highest number of Palestinians killed in a single day since late 2006.

The West Bank-based Palestinian government said Israel's "ugly crimes were a slap in the face" to efforts by Bush and the international community to resume peacemaking that would lead to the creation of a Palestinian state.

Israel said it mounted the operation to curb rocket attacks from Gaza.

Local medical workers and Hamas said 18 Palestinians  were killed in fighting with Israeli forces in the northern part of the territory and east of Gaza City.

"There was a massacre today against our people, and we say to the world that our people will not remain silent against such crimes," said Palestinian President Mahmoud Abbas, whose Fatah faction lost control of the Gaza Strip to Hamas in June.

A volunteer from Ecuador, working on an Israeli kibbutz, or farming community, bordering the Hamas-controlled Gaza Strip, was killed by a Palestinian sniper near the frontier fence. Hamas claimed responsibility for the shooting.

Israeli President Shimon Peres said as long as Gaza militants continue to fire rockets into the Jewish state, "we are left without a choice but to answer and stop it".