Pakistani security forces fought street battles with Taliban militants in the Swat Valley's main urban centre Saturday, a critical phase in the effort to wrest the northwest region near Afghanistan out of insurgent hands.

Army spokesman Major General Athar Abbas warned that the operation in Mingora town could be "painfully slow," noting some 10,000 to 20,000 civilians are still trapped there. The fight could also prove a major test for a military more geared toward conventional warfare on plains than bloody urban battles.

The military 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 the United States (US) troops in Afghanistan. For now, it appears to have broad public support in Pakistan as well.

Hard-core fighters

Abbas said 17 suspected militants had been killed in the past 24 hours of the operation in the valley. He said another major town, Matta, was cleared of militants. But some 1,500 to 2,000 insurgents remained in Swat - hard-core fighters, he said.

Mingora, which normally has at least 375,000 residents, is a major commercial centre for the valley, one the military had been preparing to enter for several days.

"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. "The pace of the operation will be painfully slow. So keep patient. But the operation has started and, God willing, we are going to take it to the logical conclusion."

The military says about 1,100 suspected insurgents have died so far in the month-old 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 also said no civilians were killed during the operation in Matta. Information provided by the military and civilians is nearly impossible to verify independently because of limited access to the region.

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.

Offensive

Pakistani Prime Minister Yousuf Raza Gilani on Saturday downplayed reports that the army would expand the offensive to the lawless, semi-autonomous tribal regions bordering Afghanistan where al-Qaida and Taliban fighters have long had strongholds.

Reports that Pakistani President Asif Ali Zardari said such an expansion was in the works have already led some families to leave the South Waziristan tribal area, the main base of Pakistani Taliban chief Baitullah Mehsud.

"It is not like this," Gilani said, in response to questions about a possible new front. "We are not foolish to do it everywhere."

It would be difficult for the army to force a fight in another territory before clearing the Taliban from Swat.

'The offensive has also triggered an exodus of nearly 1.9 million refugees, more than 160,000 to relief camps.'