Three IDF infantry battalions swept into Nablus early on Sunday in operation "Hot Winter." They sealed off the city and went house-to-house in search of terror suspects, in an operation that senior Central Command sources said could last "indefinitely." The Haruv Battalion, together with troops from the Golani and Nahal Brigades, entered the northern Samaria city, dubbed the "Palestinian terror capital" by the IDF, in a convoy of some 80 jeeps, armored vehicles and bulldozers. The operation focused on Nablus's Old City, or Casbah, a densely populated area of narrow alleyways, apartment buildings and markets. About 50,000 people were placed under curfew, residents said. The troops took over local television and radio stations, broadcasting orders to remain indoors and warning the clampdown would remain in effect for several days, residents said. The army said the road closures and curfew were necessary to prevent civilian casualties. Sporadic clashes erupted as troops discovered two major bomb laboratories containing five pipe bombs, a LAU missile, a large roadside bomb and four packs of fertilizer used for making explosives. Earlier in the day, two soldiers were lightly wounded when a bomb was thrown near their unit. They were treated at the scene. In 2006, 117 out of the 190 would-be suicide bombers captured in the entire West Bank were caught in Nablus, and nine out of the 11 suicide belts seized were found there. "This is a terror capital where all the groups work together to carry out attacks against Israel," said Brig.-Gen. Yair Golan, commander of the Judea and Samaria Division. He added that the curfew in the Casbah would continue as long as troops were operating in the city. Palestinians reported six wounded, one seriously, and at least 14 people arrested. Hospitals were surrounded by troops and ambulances had trouble reaching some of the wounded, residents claimed. Noting the low number of Palestinian casualties, Golan said troops were operating under special orders to "demonstrate restraint." He also said the residents of Nablus "were not like they used to be" and did not take to the streets in massive riots in response to the raid. IDF sources said the troops were searching for a number of suspects and planned to search most of the houses in the Casbah area for weapons and explosives. Officials said that one wanted terrorist suspect was Mehdi Abu Ghazale, head of the Nablus-based Fatah-affiliated Aksa Martyrs Brigades. Golan noted that most of the current terror alerts inside Israel originated inside Nablus, where Islamic Jihad had established its main infrastructure in the West Bank. The Shin Bet (Israel Security Agency) released for publication on Sunday that two suicide bombers were caught in the city last month. A female suicide bomber was caught near Jenin earlier this month. "There has never been a halt to Palestinian terrorism," one officer said. "While there appears to be diplomatic progress, in the field, terror is thriving." Palestinian Authority officials condemned the raid, saying it threatened PA Chairman Mahmoud Abbas's efforts to restart peace talks with Israel. "We condemn this military incursion," said Saeb Erekat, an Abbas confidante. "This will undermine the efforts that are being made to sustain the cease-fire with Israel." Also on Sunday, a smuggling tunnel under the Gaza-Egypt border collapsed, injuring three people associated with Hamas. Security officials said it belonged to a clan known for smuggling drugs and weapons. Shabtai Gold and AP contributed to the report.