Israel says it will take and control parts of the West Bank and hold them as long as Palestinian terrorist attacks persist. The Palestinian Authority says Israel's announcement is an open invitation to more violence.
An Israeli government statement released before dawn says Israel is changing the way it responds to what it calls "murderous acts of terrorists".
The statement says Israel has decided to counter terrorism by capturing territories of the Palestinian Authority. It said these areas will be held "as long as terror continues."
A senior aide to Palestinian President Yasser Arafat called the Israeli announcement an invitation to violence. Ahmed Abdel-Rahman added that any resistance to the occupation will now be legitimate. He said security for Israel would not come while Israeli soldiers occupy Palestinian land.
Palestinian witnesses say the Israeli army has reoccupied the town of Jenin and its refugee camp, and that troops are searching for suspected Palestinian militants. They say Israeli helicopters also have been firing at buildings in the area, which Israel says is a hotbed of Palestinian militant activity.
Israeli tanks and troops also carried out a pre-dawn raid on the city of Nablus and arrested a number of suspected Palestinian militants. The Israeli military says its soldiers also made several arrests in Qalqilya, the divided city of Hebron, and two nearby villages.
The operation is part of Israel's response to Tuesday's bus bombing in Jerusalem that killed 19 Israelis and wounded more than 50 others.
The radical Islamic group Hamas said its armed wing, the Izzedin al-Qassam Brigades, was responsible for the bombing. The group identified the bomber as a university student from the Al-Fara refugee camp near Nablus.
A series of similar raids into the West Bank and a recent five-week-long re-occupation have failed to put an end to the Palestinian suicide bombings.