Israeli Prime Minister Ariel Sharon said Sunday that his forces would expand their incursion into the Gaza Strip and continue the assault until the threat of rocket attacks on Israeli towns and settlements has ended.

At least 10 Palestinians were killed in fighting Sunday. And an Israeli air strike on a northern Gaza refugee camp killed at least three more Palestinian militants early on Monday, witnesses and medics said, the Reuters news agency reported.

That would push the total death toll to at least 74 since the operation began Tuesday.

Israeli tanks and armored bulldozers on Sunday flattened a kindergarten, houses and factories on the edge of Gaza's largest refugee camp, according to Palestinian medical officials and human rights organizations.

Palestinian fighters managed to launch at least three of their crude Qassam rockets into Israel Sunday, according to a spokeswoman for the Israel Defense Forces. Those attacks occurred even though more than 200 Israeli armored vehicles were swarming through the northern Gaza Strip at the time and a network of attack helicopters, fighter planes and unmanned surveillance drones patrolled the sky.

"We have to expand . . . the areas of operation in order to get the rocket launchers out of the range of Israeli towns," Sharon said in an interview on Israel Radio. He added that the operation "is not a short thing -- the forces have to remain there as long as this danger exists."

Israeli armored brigades have isolated the three major population centers in northern Gaza -- the Jabalya refugee camp and the towns of Beit Lahiya and Beit Hanoun. It had been the heaviest sustained fighting since Israeli troops entered West Bank cities in the spring of 2002 in response to a wave of suicide bombings in Israel.

Black smoke hung over Jabalya, where residents and fighters burned tires, trash and garbage in an effort to impede Israeli forces' aerial surveillance of Gaza's largest refugee camp. More than 100,000 people live there.

Israeli tanks, which were positioned near the camp entrances to try to draw fighters out of their warrens, fired throughout the day. A special correspondent for The Washington Post said Israeli forces fired toward him and other Palestinian journalists who were reporting in the camp.

More than 35 tanks and five armored D-9 bulldozers plowed through the camp's Tel Zatar neighborhood, flattening a kindergarten, at least seven houses and two factories, according to human rights groups and the Reuters news agency, which reported that posters of Donald Duck and Mickey Mouse, toys and coloring books were scattered in the rubble of the kindergarten.

"Is this place an army base or military training camp to be targeted?" Jaber Abu Oukal, the director of the kindergarten, said in an interview with the news agency. "We have 400 boys and girls, ages 3 to 5, who used to come here to play and start their first step in the educational process. Now they have no place to go but the street."

The dead in Sunday's fighting included two 14-year-olds, a 13-year-old, a deaf man who was shot by an Israeli sniper while standing on the roof of his house and four fighters, according to Moawia Hassanin, chief of emergency room and ambulance services at Shifa Hospital in Gaza City. Hassanin said Israeli forces have repeatedly fired on ambulances and medical workers attempting to remove the dead and wounded. An Israeli military spokeswoman said the defense forces have received no reports of ambulances being fired upon.

The spokeswoman said the Israeli military was investigating the death of the 13-year-old but was unaware of the reported shootings of the two other teenagers.

She said an Israeli sniper shot the man who was described as deaf because he had been seen each day on the roof of his house and was suspected of being a lookout for Palestinian fighters. One of the radicals was killed soon after he and other men fired a Qassam rocket from the Beit Hanoun area at about 1 p.m., the spokeswoman said.

Special correspondent Islam Abdulkarim at the Jabalya refugee camp contributed to this report.