4 Palestinians killed in West Bank clashes

Israeli troops killed four Palestinians in clashes in the West Bank on Saturday, including three militants who died when troops opened fire on their vehicle in the bloodiest day of fighting between the sides since January. In Gaza, assailants set off explosives at the American International School, damaging the building.

Palestinian officials condemned the West Bank violence, saying it hurt efforts to reach a cease-fire in the West Bank.

"This undermines our efforts to bring about a cessation of hostilities," said Saeb Erekat, a top aide to President Mahmoud Abbas.

Israel and Palestinian militants have been observing a cease-fire in the Gaza Strip since last November. The truce has largely held, though Gaza militants periodically fire rockets into Israel.

In talks with Prime Minister Ehud Olmert, Abbas has raised the possibility of expanding the cease-fire to the West Bank, where the army frequently conducts raids searching for wanted militants.

In Saturday's violence, Palestinian security officials said the three militants were ambushed by undercover Israeli troops in Jenin, a northern West Bank town known as a stronghold of armed groups.

They said the dead militants included two members of the Al Aqsa Martyrs' Brigades, a violent group with ties to President Mahmoud Abbas' Fatah movement, and a member of the Islamic Jihad militant group. There were no other occupants in the car.

The army said a special unit operating in Jenin came under fire from the car. It said the troops returned fire, hitting the vehicle.

Earlier Saturday, Israeli troops searched the nearby village of Kafr Dan for militants, waging several firefights with gunmen and killing one Palestinian, the army said.

Palestinian officials identified the dead man as a 22-year-old police officer who was shot by troops as he stood on the roof of his home with his brother.

The army said troops were repeatedly attacked by militants during the raid, and the soldiers fired on a man armed with a rifle standing on a roof.

Israeli Foreign Ministry spokesman Mark Regev said the Israeli operations in the West Bank help protect Israelis from attack. Numerous suicide bombings have originated in the northern West Bank. Regev said Israel tries to be "as surgical as possible" to prevent widespread fighting.

Late Saturday, Palestinian militants fired three rockets into southern Israel, including one projectile that hit a house in the border town of Sderot, Israeli police said.

Police spokesman Micky Rosenfeld said two of the rockets landed in Sderot, a frequent target of Gaza militants. Medical officials said no one was injured, but six people were being treated for shock.

No one was injured in the earlier bombing at the American International School, one of Gaza's best private schools.

Dr. Iyad Saraj, chairman of the school, said whoever was behind the attack was an "enemy of the Palestinian people."

"Our message to them is that we have decided today to challenge, to educate our children and to have a new generation that can liberate Palestine through education," he said.

The school was founded in 1995 and has more than 600 students. In March 2006, the Dutch principal and an Australian teacher were briefly kidnapped. Foreign teachers left after that incident.

The school, located near the former Jewish settlement of Dugit, was also hit repeatedly by Israeli fire during the past few years of Israeli-Palestinian fighting.