The Palestinian sources said the tanks and APCs surrounded the compound of Palestinian leader Yasser Arafat and that Israeli snipers had taken up positions around the offices. 

Members of the Israeli military searched a house along a main road in the city, the sources said, then an Apache helicopter fired a missile at the road. There was no information on casualties. 

Shortly after the incursion began, the Israeli military announced an immediate curfew for Ramallah.

The past week has seen 31 Israelis killed in three terror attacks, including two suicide bombings in Jerusalem and a shooting attack in an Israeli settlement in the West Bank. 

In Qalqilya, the Israeli military said it had cordoned off the town and troops were carrying out searches. 

Palestinian security sources said the Israeli military entered the town with 60 vehicles, including tanks and armored personnel carriers, at 4 a.m. Sunday and established a curfew and full control over the area. 

In Tulkarem, Israeli forces fired a round toward the main street, killing a man and injuring eight other people, according to the Palestine Red Crescent Society said. The Israeli army was checking the report. 

The group was leaving a mosque after night prayers when the shooting occurred, the Red Crescent Society said. 

In the village of Yamun, west of Jenin, the Red Crescent said Israeli troops killed one Palestinian and wounded another. The Israel Defense Forces had no immediate response. 

The Israeli Security Cabinet decided Friday to give the IDF the green light to re-enter West Bank towns and villages it occupied during its six-week Operation Defensive Shield action in the spring and to stay "as long as needed." 

Israeli Defense Minister Benjamin Ben-Eliezer stressed in a statement Sunday that the army would have no civil administrative control over the Palestinian population. 

Ben-Eliezer said he notified the army and the Israeli civil administration, which continues to operate in some West Bank areas, to permit wherever possible the routine activities of Palestinian civil institutions. He said the operation required "a deep and thorough action" by the army. 

Foreign Minister Shimon Peres said Sunday he hopes the Israeli occupation of Palestinian towns would not last "more than a few months." 

The IDF said one reserve brigade had been called up. After a training period, "the forces will assist regular military forces in the battle against Palestinian terror," the IDF said. 

Fence sparks debate
The Israeli Cabinet Sunday approved the route of the first phase of a 217-mile barrier designed to protect the country from suicide bombers by blocking access from the West Bank, despite strong objections from Peres. 

Construction of the first phase of the barrier, about 70 miles long (112 kilometers), began last week. 

Sharon, right, and Peres prepare for the Cabinet meeting Sunday.

The barrier will be a combination of fences, walls, ditches, patrol roads and electronic surveillance devices. The first phase of the $200 million project is scheduled to be finished within a year.  Political sources said Ben-Eliezer displayed maps of the separation fence and of Israeli security interests in the area. Part of the fence cuts into the West Bank.  Peres said the fence's presence in the West Bank could cause political damage. But Ben-Eliezer said the map of the fence line was a security map, not a political map, and Prime Minister Ariel Sharon agreed.  Peres, a member of the Labor Party, said he did not want to be part of a government that had

In another development, Palestinian security sources said without elaborating that Palestinian security services had arrested seven Hamas members in Gaza.