At least 13 Israeli soldiers died during fierce fighting Tuesday with Palestinian militants in the West Bank city of Jenin. At least 100 Palestinians have been killed during clashes over the last several days in the refugee camp in Jenin.

The Israeli military says the soldiers died in an ambush, when a booby-trapped bomb factory blew up in the Jenin refugee camp.

The army says the soldiers were on the first floor of the building, when explosives were detonated and the structure collapsed on them.

The military says that after the explosions, Palestinian gunmen opened fire on the troops from the rooftops of surrounding buildings.

It was the single deadliest incident involving Israeli forces in more than 18 months of fighting with the Palestinians.

Soldiers have been searching for Palestinian militants and weapons in the Jenin refugee camp, which has been the scene of heavy fighting during Israel's 12 day offensive in the West Bank.

Also Tuesday, Israeli forces raided the West Bank town of Dura, near Hebron, to search for wanted men. At least three Palestinians were reported killed during the raid.

Before dawn, Israeli troops pulled out of Qalqilya and Tulkarm, but soldiers are maintaining a tight blockade around the cities.

In Nablus, the Israeli military says it took control of the center of the city, where there have been fierce clashes in recent days. More than 40 Palestinians have been killed during fighting in Nablus.

In Bethlehem, a standoff continues where Palestinian militants are hiding out in the Church of the Nativity. The Israeli military is surrounding the church, but says it will not attack the holy site, where tradition says Jesus was born. Palestinian gunmen inside the Christian shrine are refusing calls to surrender.

Israel launched its massive military operation in the West Bank after a series of Palestinian suicide bombings killed dozens of Israelis. Israeli Prime Minister Ariel Sharon says the military operation will continue until Palestinian militant groups are crushed.

The Jewish state has been under pressure from the United States and other countries to withdraw from Palestinian-ruled areas.

U.S. Secretary of State Colin Powell is expected to arrive in Israel later this week in an effort to broker a cease-fire.