Palestinian militants fired five makeshift rockets into southern Israel as Prime Minister Ariel Sharon (search) visited the area Tuesday, a salvo that came despite the launch of an Israeli offensive meant to halt such attacks.

The rockets, which wounded one man, were fired a day after a rocket attack killed two Israelis, including a 3-year-old boy, in the border town of Sderot (search).

A senior official said Sharon was in the town to visit the boy's family and was not harmed.

"We don't plan to ignore what happened here. The security services have begun taking actions whose aim is to prevent the firing of these missiles," Sharon said.

It was unclear whether militants knew Sharon was in the area.

The pre-dawn Israeli military operation came in response to the Sderot attack, the first time in nearly four years of fighting that the crude homemade Qassam rockets (search) killed Israelis.

Under the cover of intense machine gun fire, Israeli tanks and bulldozers blocked roads in the northern Gaza Strip (search) early Tuesday — the start of what security officials said could be an extended operation in the area.

"After this takeover, the ability to launch Qassams will be diminished," Defense Minister Shaul Mofaz said during a tour of an army base in northern Israel. His comments were reported on the Web site of the Haaretz daily.

Five people were wounded by Israeli gunfire, Palestinian security sources said. The militant group Hamas said one of its members had died accidentally while handling explosives. The Israeli army had no comment.

Elsewhere in Gaza, troops killed a 15-year-old boy in the Khan Younis refugee camp, Palestinian hospital and security sources said. The army did not comment.

Despite the surge in violence, Sharon said Monday that he remains determined to withdraw from Gaza in 2005 and pledged to speed up the evacuation of Israeli settlers who are ready to leave voluntarily.

Sharon's vice premier, Ehud Olmert, said Israel will continue to strike at militants even as plans for the withdrawal proceed. "There is a war against terror, and we shall continue fighting terror regardless of disengagement," he said.

The Israeli army said the militants had used a new, upgraded version of the Qassam in the attacks on Monday and Tuesday.

A military official said the so-called Nasser 3 rockets are more accurate and pack more explosives than previous versions, potentially causing as much damage as a suicide bombing. "This has become a significant threat," the official said, speaking on condition of anonymity.

Continued rocket attacks could weaken the broad public support in Israel for Sharon's withdrawal plan.

The Israeli operation Tuesday was focused around the town of Beit Hanoun in northern Gaza.

By midmorning, the army had sealed all entrances to the town. A bulldozer moved piles of sand near one of the exits, and an Apache helicopter hovered overhead.

Beit Hanoun has been repeatedly targeted in army raids in the past. The town is less than one mile from Sderot, and militants have repeatedly launched missiles from the area.

In previous raids, the army demolished scores of homes and uprooted thousands of trees, saying it was trying to deprive cover for those firing rockets.

"I oppose those who are firing rockets, and I don't like violence at all," said Jaber Saeda, a 42-year-old farmer who said his greenhouses had been destroyed by Israel last year.

"But how can I convince my children and myself that the Israelis are serious about peace when I see them uprooting trees and destroying houses and killing our children?" he said.

Israeli security officials, speaking on condition of anonymity, said troops would likely stay in northern Gaza for an extended period.

Over the weekend, Palestinian militants dug a 1,000 foot-foot-long tunnel and detonated hundreds of pounds of explosives underneath an army outpost, killing a soldier and wounding five others.

Hamas has claimed responsibility for the recent attacks, and the Al Aqsa Martyrs' Brigades (search) said it participated in blowing up the outpost.

In an initial response, Israeli helicopters fired missiles at a Hamas-linked media center in a 16-story building in Gaza City and a metal workshop in a refugee camp early Tuesday. The army said rockets were being made at the workshop.

The army also blew up an empty eight-story building and razed 15 homes near the outpost. The demolitions left about 60 Palestinians homeless.

About 2,500 Hamas supporters celebrated the outpost attack in a rally Monday evening in the Gaza refugee camp of Jabaliya. Speakers said attacks on Israel would continue.

Sharon's "unilateral disengagement" plan calls for the evacuation of all Gaza Strip settlements — where some 7,500 Israelis live among 1.3 million Palestinians — and four West Bank enclaves by September 2005.