A major Pakistani military offensive in the northwest has killed up to 700 militants in the past four days, and the operation will proceed until the last Taliban fighter in the area is ousted, the country's top civilian security official said Monday. The offensive in Swat and surrounding districts has earned praise from the US, which wants al-Qaida and Taliban militants rooted out from Pakistani havens where they can plan attacks on American and NATO forces in Afghanistan. But the fighting has unleashed an exodus of refugees, and raised concern over the future of nuclear-armed Pakistan. Interior Minister Rehman Malik's announcement of 700 militants killed came as a witness and a police official reported new airstrikes in parts of the Swat Valley, a one-time tourist haven that fell prey to Taliban advances two years ago. Malik's toll - which exceeds that given by the military on Sunday by at least 200 - could not be independently confirmed. "The operation will continue until the last Talib," Malik said. "We haven't given them a chance. They are on the run. They were not expecting such an offensive." On Sunday, a suspension of a curfew allowed tens of thousands more civilians to leave Swat for safer parts of the northwest. The UN said Monday that 360,600 displaced people had registered in camps and centers since May 2 after fleeing Swat and neighboring Dir and Buner districts. That's on top of some 500,000 people registered as displaced due to past offensives - a major humanitarian test for the weak government. The military has relied heavily on air-strikes since the offensive in Swat began full-scale on Thursday, and it was unclear how authorities identified the militant dead. Authorities have yet to say how many civilians have been killed or wounded, possibly for fear of causing a public outcry. The army's top spokesman said Sunday that so far some 400 to 500 militants had died. But Malik said the figure was closer to 700, and that it was expected to "rapidly rise." Jawad Khan, a university student who lives in the Kabal area of Swat, said jets bombed the nearby Dhada Hara village Monday morning. "I saw smoke and dust rising from the village," Khan said, adding he didn't know about casualties because of curfew restrictions, which have been enforced again. A police official said jets bombed the Matta area of Swat on Monday as well. The official said he was confined to his station but could see a decapitated body lying outside along a road where a clash between military forces and the Taliban on Sunday left six militants dead. He requested anonymity because of security reasons. He also said that information he had received indicated the militants retained control of Swat's main town, Mingora. The military responded with force to the Taliban last month after the insurgents in Swat tried to impose their reign in other neighboring areas, including a stretch just 100 kilometers from the capital, Islamabad. Swat lies near the Afghan border as well as the wild Pakistani tribal areas, where al-Qaida and the Taliban have strongholds and where US officials believe al-Qaida chief Osama bin Laden may be hiding. The army says 12,000 to 15,000 troops in Swat face 4,000 to 5,000 militants, including small numbers of foreigners and hardened fighters from the South Waziristan tribal region. Many in the northwest have little faith in the government's ability to help them, a challenge to Pakistan's leaders because disillusioned refugees could prove fertile recruiting ground for the Taliban. Malik said the government was providing sufficient funds to help the displaced Pakistanis, and brushed aside fears that militants would try to infiltrate relief camps. "This fear is baseless that they are melting down among the displaced people because we are screening the displaced people," he said. "We are registering them with documents, checking each and every individual." Elsewhere in Pakistan's northwest on Monday, a suicide bomber exploded his vehicle at a checkpoint, killing four civilians and a member of the Frontier Constabulary security force, police said. The bombing occurred between the main northwest city of Peshawar and the town of Darra Adam Khel, police official Arif Khan said.