Jerusalem ? Israeli tanks moved early today into central Gaza, witnesses said, killing seven people and destroying two houses. Troops also arrested two members of the Islamic Hamas militant group.

The incursion into the Nusseirat and Bureij refugee camps followed pledges by Israeli officials to crack down on militants from the violent Hamas group. The Israeli military would say only that an operation was in progress.

Witnesses said the focus of the incursion was the Bureij camp, where soldiers blew up two houses after demanding that residents leave.

The army has adopted a policy of destroying the houses of militants who carried out or orchestrated attacks against Israelis. Palestinians complain that innocent relatives suffer as a result.

Palestinians said at least two of those killed were civilians — a 14-year-old boy shot dead and a woman whose house collapsed from the force of the blast next door. The bodies of the dead were still in the camp, residents said, and dozens of people wounded from Israeli gunfire were lying untreated in the streets.

Two Hamas leaders were arrested by Israeli forces, Palestinians said. The leaders were identified as Mohammed Taha, a Hamas founder and leader of the group in the Nusseirat camp, and his son.

Israeli Defense Minister Shaul Mofaz said Sunday that Israel would step up its military operations in Gaza aimed at Hamas, which has claimed responsibility for dozens of attacks, including the bombing of an Israeli tank in Gaza two weeks ago that killed four Israeli soldiers.

Israel’s new Cabinet ministers officially took office Sunday, bringing to power a hawkish government that appears set to continue using tough military measures to suppress the 29-month-old Palestinian uprising.

Israeli media on Sunday reported the arrest in Bethlehem of a member of a Hamas cell that allegedly planned to explode a bomb near Sharon’s motorcade and to attack a synagogue. The reports said the militant, identified as Fahdi Murtaja, was arrested on Feb. 7.