By Khalid Qayum and Naween Mangi Oct. 17 (Bloomberg) -- Pakistan’s military began a ground and air offensive against Taliban guerrillas in their stronghold of South Waziristan, its most direct attempt to end terrorist violence that has threatened to destabilize the government of the nuclear-armed state. The operation started late yesterday, said an army spokesman, who declined to be identified in accordance with military policy. The operation may take eight weeks or longer to complete, he said. Troops will target both Pakistani and foreign militants, he said. Fighters loyal to the late Baitullah Mehsud have led an escalating campaign against President Asif Ali Zardari’s administration. The U.S. has encouraged offensives against Pakistan-based Taliban, saying Waziristan and other border districts are sanctuaries for jihadists who attack U.S.-led troops in Afghanistan. A Pakistani news channel, Express News, reported that residents were continuing to leave the mountainous region as fighting began. Thousands of displaced people have reached the nearby city of Dera Ismail Khan, where they are being registered at the main sports stadium, the network said. Northwest Frontier Province Information Minister Mian Iftikhar Hussain said as many as 2 million families may be displaced as a result of the military operations South Waziristan. He spoke in televised press conference in Peshawar today. He didn’t say what plans the government has for housing the displaced people. Deaths Four Pakistani soldiers were killed and 12 injured in initial clashes with militants, the military said in a statement on its Web site. A bomb exploded near a military convoy as it moved from Razmak, a military base in North Waziristan, Agence France- Presse reported. While the agency said two soldiers were killed, that was not confirmed by the army statement. Razmak is one of four main launching points for the offensive, to the north, east and west of Mehsud’s forces, Pakistan’s Samaa television said. The government said last week it had approved an offensive and given authority to the army chief, General Ashfaq Parvez Kayani , to decide when to launch it. The army says it has deployed 28,000 troops around South Waziristan to attack an estimated 10,000 fighters of a major Taliban faction led until August by Baitullah Mehsud . Mehsud Mehsud was killed in August by a missile from a U.S.- operated unmanned aircraft, and his forces now are led by a relative, Hakimullah Mehsud. While other Taliban factions have focused their attacks on NATO forces in Afghanistan and their Afghan government allies, the Mehsud fighters have waged an escalating campaign within Pakistan. Pakistan’s government blamed Baitullah Mehsud for the 2007 assassination of former Prime Minister Benazir Bhutto , the wife of President Zardari, an accusation Mehsud denied. Spokesmen for the Mehsud Taliban have claimed responsibility for a spate of bombings and guerrilla assaults this month against government, army and police targets. At least seven guerrilla attacks in the past week have killed 140 people, including 11 who died in a car bombing yesterday in the northwestern city of Peshawar. Pakistan’s Taliban and their allies also are turning to commando raids on police and soldiers as a tactic to convince Pakistanis the government can’t contain them. At least 26 people were killed in assaults on Oct. 15 on a federal police headquarters and two police training centers in the eastern city of Lahore, and a bombing at a police station in Kohat. Commando Assaults While suicide bombings killed most of those who died in the past week, the Pakistani media’s focus has been on the commando assaults Oct. 15 and a 22-hour siege last weekend at Pakistan’s army headquarters in Rawalpindi. Jihadists also used commando assaults in Lahore in March, against a bus carrying the Sri Lankan cricket team and at a police academy that was attacked again on Oct. 15. The tactic has been revived in an effort to fight back after the army drove the Taliban out of the Swat Valley in July and killed Mehsud in August, said Kamran Bokhari, regional director for the Middle East and South Asia at Stratfor , an Austin, Texas- based intelligence-consulting firm. The week-long spate of attacks is in part an effort to demoralize Pakistan’s security forces in advance of the offensive begun today, Bokhari said. To contact the reporter on this story: Khalid Qayum in Islamabad at kqayum@bloomberg.net or Naween A Mangi in Karachi at nmangi1@bloomberg.net