Gunshots pierced the air as Pakistani troops battled Taliban fighters in Swat Valley's main city, while thousands of civilians hid in their homes, a witness said - pushing the fight to a critical phase in the effort to wrest the region out of insurgent hands. The army has pushed into Mingora, where it says some 10,000 to 20,000 residents are stranded in the city as soldiers fight street-to-street against insurgents. "I will try to leave again whenever I get another chance," Fazal Wadood, 45, a local political party leader, told The Associated Press by telephone on Saturday night. "It is like inviting death to stay here anymore." The monthlong operation in Swat and surrounding districts has strong support from Washington, which wants Pakistan to root out insurgents who use its territory to plan attacks on US troops in Afghanistan. But the fight in Mingora could also prove a stiff test for a military more geared toward conventional warfare on plains than bloody urban battles. Army spokesman Maj. Gen. Athar Abbas said Saturday that retaking the city was likely to be "painfully slow" because of the continued presence of civilians it wants to avoid harming. "The terrorists are going to use (civilians) as human shields. They are going to make them hostage, so we are moving very carefully," Abbas said. Mingora, which normally has at least 375,000 residents, is a major commercial center for the valley. Most of them have already fled. Wadood, a leader of the opposition Pakistan Muslim League-N party, said the gunfire Saturday was at first continuous before coming at intervals. He said he had tried to flee the city twice already but failed due to the fighting and lack of transportation. Around 3,000 to 4,000 people are still trapped in his neighborhood near the emerald mines on the outskirts of the city, he said. The military says about 1,100 suspected insurgents have died so far in the offensive. It has not given any tally of civilian deaths, and it's unclear how it is separating regular citizens killed from militants. Residents fleeing the region have reported dozens of ordinary Pakistanis killed in the fight. Abbas said that some 1,500 to 2,000 hard-core insurgent fighters remained in Swat. Information provided by the military and civilians is nearly impossible to verify independently because of limited access to the area. The offensive has also triggered an exodus of nearly 1.9 million refugees, more than 160,000 to relief camps. Some fear the generally broad public support for the military campaign could drain away if the refugees' plight worsens or if the army gets bogged down too long. Officials have downplayed reports that the army would expand the offensive to the lawless, semiautonomous tribal regions bordering Afghanistan where al-Qaida and Taliban fighters have long had strongholds. However, violence has continued to flare in those areas. It would be difficult for the military to launch another major offensive before clearing the Taliban from Swat. Pakistan's army has long been more structured around fighting a conventional battle against rival India on the plains of the Punjab region using tanks and artillery. It has limited experience battling guerrillas in urban settings. Many Taliban fighters can simply blend into the population or melt away to the hillsides. On Sunday morning in the Orakzai tribal region, helicopter gunships pounded militant locations, including a religious school, killing at least five insurgents.