Israel killed at least 18 Palestinians, nearly all Hamas militants, in the Gaza Strip yesterday, in violence the Palestinian Authority said was a "slap in the face" to US President George W. Bush's peace efforts. 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 shooting the man.

The violence, four days after Bush ended a visit to Israel and the occupied West Bank, resulted in the highest number of Palestinians killed in a single day since late 2006. Israel said it mounted the operation to curb rocket attacks from Gaza.

Hamas's armed wing claimed responsibility for firing rockets into Israel on Tuesday for the first time since the Islamist group routed Palestinian President Mahmoud Abbas's Fatah forces to take control of the Gaza Strip in June.

Hamas had fired mortar bombs and allowed other Palestinian militant groups to fire rockets into Israel, but the direct claim marked a more aggressive approach towards the Jewish state.

Local medical workers and Hamas said 18 Palestinians - 13 Hamas men, three other militants and two civilians - were killed in fighting with Israeli forces and a series of missile strikes in the northern and eastern Gaza Strip.

"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 Mr Abbas.

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