Israeli army officials said the helicopter strikes were a "limited action designed to respond to the barbaric act Palestinians conducted yesterday morning." Deputy Defense Minister Ephraim Sneh said Israel did not intend to "conquer" territory in the West Bank and Gaza Strip under Palestinian security control.

But the assault showed that Israel was prepared to use heavy weaponry the Palestinians do not possess.

The Israeli helicopter assaults first targeted the police station where the Israeli soldiers were killed and the Palestinian TV headquarters in Ramallah. At least 12 people were injured, Palestinians said.

In Gaza City, Arafat's headquarters and buildings near it were hurriedly evacuated. Shortly afterward, a guard house next to the residence was hit, and smoke rose above the compound.

In Ramallah, the police station was reduced to rubble after being hammered by the rockets, and flames poured out of a second building. An angry mob gathered outside the station, shouting "God is great" and raising a Palestinian flag on a damaged wall.

Fighting continued into the night as combat helicopters attacked the main compound of the Palestinian security forces in Nablus. Police officers fled into the street before the shooting began. A firefight erupted in the West Bank town of Hebron, and gunships attacked soldiers in the town of Salfit near Nablus.

Israel also clamped an internal closure on the West Bank, meaning Palestinians could not leave their communities.

In another development, the Palestinian Authority released hundreds of prisoners, including scores of Islamic militants, from jails in the West Bank and Gaza Strip.