NABLUS, West Bank, (AP) -Israeli troops sealed off the center of Nablus’ old city with cement blocks and trash containers Monday, and searched apartments for seven Palestinian fugitives whose names the army broadcast over local TV and radio stations.

It was the largest Israeli raid in the West Bank in months, with about 80 jeeps, armored vehicles and bulldozers moving around Nablus for a second day. Troops enforced a curfew that confined tens of thousands of Palestinians to their homes.

Soldiers uncovered two explosives labs in what the army said would be an open-ended sweep. Palestinian officials charged that the offensive threatened efforts to restart peace negotiations.

On Monday, soldiers operated simultaneously in several areas of Nablus, including the old city, or casbah, a densely populated militants’ stronghold with small alleys.

Mohammed Attireh, 47, who lives in the area, said all the residents of his building were ordered to stay in his apartment while troops searched the other apartments. Then the group of more than 20 people was taken to another house, while soldiers searched his apartment.

Attireh said troops took over two houses on his street as temporary positions, and that almost every house in the neighborhood was searched.

Seven members of the Al Aqsa Martyrs’ Brigades, a violent offshoot of the Fatah movement of Palestinian President Mahmoud Abbas, were the apparent target of the raid. In a new tactic, troops broke into transmissions of local TV and radio stations Sunday and broadcast the names of the men, all residents of the old city. Soldiers warned civilians against hiding the fugitives.

Abir Kilani, director of the local TV station Gama, said her broadcasts were interrupted several times by the army. Kilani noted that this method is much more effective and cheaper than the military’s previous tactic of dropping leaflets over Nablus.

In another area of the city, soldiers surrounded a three-story residential building Monday, but did not encounter resistance or find wanted men. One apartment was burned in the operation, witnesses said.

Dozens of Al Aqsa gunmen operate in Nablus, organized in small groups with a central authority. Residents have complained that some of the gunmen are terrorizing the city by settling personal scores in shooting attacks, acting as self-appointed vice squads or engaging in black mail.

Two Al Aqsa gunmen, brothers Ahmed and Alaa Sanakra, said all fugitives had gone into hiding, but were communicating with each other. Alaa Sanakra said the Israeli raid helped unite the splintered groups, but left the gunmen worried.

The Nablus operation began before dawn Sunday, with bulldozers closing main roads with piles of rubble. Soldiers ordered residents to remain indoors and said the clampdown would remain in effect for several days.

The army said the road closures and curfew were necessary to avoid civilian casualties.

During house-to-house searches Sunday, soldiers at one point forced a Palestinian youth to lead them into a home. The soldiers then took him, along with several young Palestinian men, into a military vehicle.

Attireh, the old city resident, said he was also ordered by troops to lead the way and knock on the door of a neighboring home — only to find soldiers inside.

In 2005, Israel’s Supreme Court banned the practice of using Palestinian civilians as “human shields” to search homes for explosives or militants ahead of soldiers. The army had no immediate comment on Sunday’s incident, which was filmed by Associated Press Television News.

Sporadic clashes were reported as soldiers were pelted with stones and cement blocks, and exchanged fire with Palestinian gunmen, the army said. Two soldiers and four Palestinians were wounded.

The raid came a day after Israeli troops discovered an explosives laboratory in the city, the West Bank’s commercial center, and Maj. Avital Leibovich, an army spokeswoman, said the soldiers uncovered another explosive lab and small caches of weapons on Sunday.

Area commander Brig. Gen. Yair Golan said the military entered Nablus because of increased militant activity there. He said most of the intercepted bombers and explosives came from Nablus.

“We entered the city to lower the threat level to Israel and hit terror infrastructure,” he said in a telephone interview.

Palestinian officials said the raid threatened new peace efforts. “This will undermine the efforts that are being made to sustain the cease-fire with Israel,” said Palestinian negotiator Saeb Erekat.

The raid came at a sensitive time for Abbas, who is trying to put together a unity government with the Islamic militant Hamas group.

In other developments, an Israeli settler was found stabbed to death Sunday night near his settlement of Bat Ayin, about eight miles from the West Bank city of Hebron, and police said he was killed by Palestinian militants. There was no claim of responsibility.

Police spokesman Micky Rosenfeld said police and army squads were combing neighboring Arab villages, but no suspects had been arrested.