Fierce fighting erupted Saturday in Pakistan's lawless South Waziristan tribal region that borders Afghanistan, when government forces launched a much-awaited ground offensive against Taliban insurgents, according to dpa. "The main objective of the operation is to eliminate terrorists," said Major General Athar Abbas. "The operation will continue for six to eight weeks." The security head of the tribal region, of which South Waziristan is a district, said the ground forces were being supported by the Air Force. An intelligence official who spoke on condition of anonymity said ground troops, backed by tanks and artillery, were facing stiff resistance from the militants. "Taliban have also taken positions in the mountains and they are targeting our troops from underground bunkers in the forests," he added. A roadside bomb exploded next to an army convoy in the Jandola area of South Waziristan, killing two soldiers and injuring five more, the intelligence official said. A similar blast killed one soldier and injured three in the neighbouring North Waziristan district. Eleven militants died when the military jet destroyed two hideouts in South Waziristan, where more than 1,500 al-Qaeda fighters are also participating in the fighting, according to intelligence officials. Thousands of families were fleeing the conflict. According to the United Nations, some 80,000 people had so far been displaced since May, when the Pakistani jets started airstrikes to soften militant positions. Humayon Khan, the commissioner of Dera Ismail Khan district that borders South Waziristan, said the government expected the numbers of internally displaced people might reach 120,000. "We have set up four centres in Dera Ismail Khan where the (refugees) are being registered," he added. The operation comes after a series of suicide attacks at security installations across the country that left more than 160 people dead, many of them civilians, in less than two weeks. The brazen strikes also involved a hostage drama at the Pakistan Army's headquarters in the garrison city of Rawalpindi, located adjacent to the capital Islamabad. Twenty-four people, including nine raiders, died in the 22-hour standoff. The leader of the assailants was arrested. The army says more than 30,000 soldiers were pitched against 10,000 to 15,000 well-trained and well-equipped guerrilla fighters in the rugged mountainous district. The offensive is aimed at fighters loyal to Baitullah Mehsud, the former Taliban chief who died in a US drone strike in early August. Mehsud's men are considered as a domestic threat to Pakistan as compared to other groups of Taliban that concentrate on carrying out "resistance against foreign invaders" in Afghanistan. Recent opinion polls show Pakistani public is broadly supportive of military action. The country's political leadership - the ruling as well as the main opposition political parties - have demonstrated unity with the army taking on the militants. But the support could evaporate if the militants manage to prolong the fighting and carry out more terrorist attacks in the urban centres.