Witnesses said the raid began before sunrise as tanks, armored personnel carriers and bulldozers rolled into the town, and then moved to the western part of the Jenin refugee camp.
In the refugee camp, which had been the scene of fierce fighting during Israel's recent West Bank offensive, Israeli forces surrounded the house of a militant belonging to the Islamic fundamentalist group Hamas and ordered him outside, the witnesses said.
They said the militant, Jamal Abu al-Haija, did not appear, but his wife and children exited the house. Soldiers then threw hand grenades into the dwelling, and the house caught fire.
The Fatah movement's secretary in Jenin, Qadoora Mousa, told United Press International that the Israeli army arrested about 30 Palestinians from Jenin.
Those arrested included Kamal Abu El Wafa, leader of Palestinian leader Yasser Arafat's Fatah movement in Jenin, Mousa said. He added that Israeli troops raided several buildings in the town.
In April, the Israeli army carried out the toughest ever operation into the West Bank in what it called Operation Defensive Shield, which Israel said was aimed at routing out militants and their infrastructure. During that military offensive, Jenin refugee camp was besieged.
The Israeli army left the refugee camp under international pressure, but dozens of Palestinians were killed and hundreds were left homeless after their homes were destroyed. About two dozen Israeli soldiers were killed.
In other developments, medical Palestinian sources at Shifa Hospital in Gaza City said Friday that Israeli troops fatally shot a young Palestinian man near the Jewish settlement of Dogit in the northern Gaza Strip.
The sources said the young man was apparently shot by Israeli troops stationed near the settlement. Palestinian security sources denied Israeli army allegations that the man had been trying to infiltrate the settlement.
Officials of Arafat's Palestinian Authority have said that hundreds of civilian residents of Jenin refugee camp were killed in Israel's Operation Defensive Shield.
Amnesty International had said that it found preliminary evidence that Israeli soldiers violated the Geneva conventions and other laws of war, for instance using civilians as human shields, denying medical assistance to the wounded, deliberately targeting ambulances and demolishing homes while their residents were still inside.
The Israeli military denied that it carried out a massacre and asserted that its three-week incursion into the camp was necessary to "uproot an infrastructure of terror." It said it tried to minimize civilian casualties --- for example, eschewing the use of air power --- and in doing so, put the lives of its soldiers at risk.
Israel said the camp was a legitimate military target and that armed Palestinians broke the laws of war by booby trapping homes, using ambulances to transport fighters who were not wounded and deliberately taking shelter among civilians.
Twenty-three Israeli soldiers died in the incursion, and the bodies of scores of Palestinians were recovered. U.S. Secretary of State Colin Powell said "a great deal of destruction" was visited on the camp by Israeli armored bulldozers --- which U.N. officials say left more than 1,000 residents homeless --- but that he had "yet to see evidence of a massacre."