Israeli warplanes sent missiles slamming into a car carrying Hamas militants and a load of weapons yesterday in Gaza City, killing three people, then demolished arms factories belonging to two Palestinian militant groups, the army said.

In Jerusalem, Prime Minister Ehud Olmert threatened tougher action if intensified Palestinian rocket fire on Israeli border communities did not cease.

The sixth straight day of airstrikes came as an uneasy truce between warring Palestinian factions set in after a week of fierce fighting. Masked Hamas and Fatah gunmen who had controlled the streets and taken over apartment buildings in the previous week scaled back their presence sharply, and residents who had holed up at home seeking refuge from the gunbattles ventured out to stock up on supplies at busy shops.

Children went back to school in time for final exams, and adults returned to work.

Bilal Qershali, a 31-year-old technician at the Communications Ministry, discovered that computers at the ministry had been stolen and damaged, and office furniture destroyed by gunmen who had taken over the building during the week of fighting. The damage was so severe that he and some 300 other employees left shortly after arriving, Qershali said.

"Life is back to normal, but the effects will remain," he said.

Four previous truces last week quickly collapsed, but Hamas spokesman Fawzi Barhoum said he expected the cease-fire deal reached on Saturday to stick because of Israel's military action.

"No one would condone fighting one another while the Israelis are shelling Gaza," he said.

More than 50 Palestinians were killed in clashes that broke out after Palestinian President Mahmoud Abbas of Fatah stationed thousands of loyalist security forces in Gaza City without consulting Hamas, Fatah's partner in the Palestinian governing alliance.