GAZA CITY, Gaza Strip - Israeli troops battled Palestinian militants into the early hours of Friday morning in the northern Gaza Strip, killing five militants overnight and threating to bulldoze houses from which shots were being fired, hospital officials and residents said.

In a separate operation, an airstrike on a car in Gaza City killed three Hamas members travelling inside,one of them a local militant commander, witnesses said. An army spokeswoman said a vehicle carrying "terror activists" was hit.

A total of 20 Palestinians, mostly militants, have been killed in and around the northern town of Beit Hanoun since Wednesday, when Israeli attack helicopters, tanks and ground troops launched the military's biggest push in months to stop Palestinian rocket fire.

Hospital officials said five gunmen were killed there and scores wounded by air strikes and ground fire since nightfall Thursday. The military said aircraft hit rocket launch sites and in one case fired at a group of gunmen laying explosive charges in the path of army vehicles.

Earlier Thursday in Beit Hanoun, two militants,an elderly civilian,and a police officer were killed in the fighting.

On Wednesday, 10 Palestinians were killed in Beit Hanoun and scores wounded, many of them militants battling Israeli forces. Hospital officials said a four-year-old boy wounded in Wednesday's shooting died early Friday morning.

Israeli officials have said the takeover of Beit Hanoun was expected to last only a few days and did not signal the start of a wider-scale military offensive in Gaza.

The Israeli army said more than one-third of the 800 rockets fired at Israel in recent months were launched from Beit Hanoun.

Despite the offensive, militants fired six rockets at Israel from northern Gaza on Thursday, the military said. Two Israelis were slightly wounded and a house was damaged.