Jerusalem ? Gunmen shot and killed two Israeli security guards Saturday at a construction site for the disputed barrier that Israel is erecting along its frontier with the West Bank.

The incident occurred hours after Israeli troops shot dead two Palestinians, including a 10-year-old boy, after a stone-throwing clash in the West Bank escalated into a gun battle with militants.

All four killings underscored the daily violence that has characterized the three-year-old conflict, which has killed more than 2,500 Palestinians and almost 900 Israelis. The new bloodshed came as efforts were underway to craft a cease-fire deal and restart frozen peace talks.

The two Israeli security guards were sitting in their car, keeping watch over heavy equipment that was being used to prepare the way for a Jerusalem-area section of the barrier.

They were shot at close range after dark on Saturday, and their weapons were stolen, Jerusalem Police Chief Micky Levy said. Three other security guards arrived and fired shots as the assailants fled.

The Jenin Martyrs Brigade, a militant group believed to be linked to Palestinian leader Yasser Arafat’s Fatah faction, claimed responsibility for the shooting in a statement faxed to news media.

Israeli Foreign Ministry spokesman Daniel Taub criticized the Palestinian leadership for not doing more to stop attacks and dismantle violent extremist groups.

“This is another tragic loss of life,” Taub said.

Palestinians have vehemently opposed Israel’s construction of the fence, which in places cuts into the West Bank, cutting off Palestinian land. Israel says the barrier is needed to prevent suicide bombers from entering its territory.

In the West Bank Saturday, about 35 Israeli peace activists traveled to the Palestinian village of Einabus with olive tree saplings to show their sympathy over the cutting of 250 olive trees there last month, apparently by Jewish settlers in the area.

Village resident Fawzi Hussein said the Israeli activists wanted to plant six olive saplings next to the grove where his trees were cut but the army would not let anyone into the area, calling it a closed military zone.