Fighting and military activity in West Bank and Gaza

JERUSALEM (CNN) -- A summary of fighting and military activity in the West Bank and Gaza late Friday and Saturday:

Israeli troops backed by helicopter gunships waged fierce battles in Nablus Saturday with Palestinian gunmen and conducted house-to-house searches, according to Palestinian residents and local officials. Israeli troops searched the home of the city's mayor, who was out of town, and they arrested his two sons, they said. The Israeli army reported fighting in the city but gave no immediate details.

Near Nablus, the Israel Defense Forces said it killed four terrorists Friday night caught laying explosives near an IDF checkpoint at the Askar refugee camp. Palestinian medical sources confirmed the four deaths.

Israeli troops were bulldozing through houses in the Jenin refugee camp, after Palestinians put cement barricades in the camp's entryways in anticipation of the Israeli incursion, Palestinian sources said. An Israeli army officer said they had control of the city of Jenin after "difficult fighting" as part of Israel's anti-terrorism operation. The army's last stage was controlling the Jenin refugee camp.

In a separate incident near Jenin, Israeli troops shot a Palestinian with an explosive belt late Friday. Israeli sources said the device he was carrying exploded and the man was killed. No IDF soldiers were injured in the explosion. At least 50 houses have been damaged in the incursion into Jenin, according to Palestinian sources.

Chief Palestinian negotiator Saeb Erakat told CNN he lost contact with Arafat -- who remains holed up inside the compound -- around 3 a.m. Saturday, but communication was restored by the afternoon. He said the situation inside the compound, where Arafat and 40 others remain holed up, was OK, although there was no electricity or running water and food supplies were low.

Erakat said the last message from Arafat indicated "sounds of explosions in the building," however the Israel Defense Forces said there was no shooting toward Arafat's offices.

The helicopter strike took place in the town of Tubas, between Nablus and Jenin. Six members of Izzedine al Qassam -- the military wing of Hamas -- were killed. The U.S. State Department has labeled Hamas a terrorist organization.