MARDAN, Pakistan (AP) -- Pakistan's army vowed Friday to eliminate militants from a northwestern valley but warned that its under-equipped troops face thousands of Taliban extremists who have seized towns, planted bombs made from pressure cookers, and dragooned children to be suicide bombers.
As air force jets roared overhead and gunbattles raged, terrified civilians from the Swat Valley and neighboring districts accelerated their exodus, with U.N. and Pakistani officials predicting 1 million refugees will soon burden the turbulent Afghan border region.
Washington describes the militants as an existential threat to nuclear-armed Pakistan itself, as well as to U.S. chances of destroying al-Qaida or of winning the war against their insurgent allies in neighboring Afghanistan.
"The army is now engaged in a full-scale operation to eliminate the militants, miscreants and anti-state elements from Swat," said Maj. Gen. Athar Abbas, chief army spokesman. "They are on the run and trying to block the exodus of civilians from the area."
There are doubts about the ability and resolve of the army and the government to sustain the kind of grinding counterinsurgency warfare needed to defeat extremists whose rhetoric resonates widely in a Muslim nation deeply skeptical of U.S. goals in the region.
Abbas sought to counter portrayals of the military as ill-trained, saying that they had learned a lot in eight years of fighting along the border. But he said they need helicopters, surveillance drones and night-vision equipment, which the U.S. is scrambling to provide.
Pakistan's army is fighting to wrest Swat and two neighboring districts from militants who dominate the adjoining tribal belt along the Afghan frontier, where U.S. officials say al-Qaida chief Osama bin Laden is likely holed up.
The army announced its offensive after Prime Minister Yousuf Raza Gilani said the government would wipe out groups trying to "take Pakistan hostage at gunpoint." Battles and bombing runs by helicopters and jets have been going on all week.
Abbas said Friday that more than 140 militants and two soldiers had been killed in Swat in the last 24 hours - roughly doubling the number of casualties reported so far.
The latest figure included 100 militants killed in bombardments of remote training camps and arms dumps. Abbas didn't explain how the body count was done. Fighting in neighboring Buner and Lower Dir killed another 31 militants and three soldiers, he said.
Officials say they are unable to confirm accounts from fleeing civilians of innocents killed and wounded by indiscriminate gunfire and shelling. Abbas said troops were advancing slowly to try to minimize such collateral damage.
But the stream of civilians seeking safety appeared to have intensified, leaving Pakistan facing a humanitarian emergency.
The mayor of Mardan, the main district to the south of the fighting, said an estimated 250,000 people had fled in recent days. Of those, 4,500 were staying in camps, while the rest were with relatives or rented accommodation, he said.
On Friday, the U.N. refugee agency said provincial officials had told them 500,000 had fled, were on the move, or were trying to flee. About a half-million have already been made homeless elsewhere in the border region since August 2008, when the army launched its last major anti-Taliban operation in the Bajur border region.
Tens of thousands of people are trapped in Mingora, Swat's main town. Some have accused the Taliban of not allowing them to leave, perhaps because they want to use them as human shields. Others came under attack even as they fled.
Siraj Muhammad, a 19-year-old mechanic among the exhausted multitude who made it to Mardan on Friday, said a shell exploded near people trying to walk to safety, killing two and wounding him, his mother and two siblings.
After struggling on for several miles, they flagged down a truck, joining scores of others escaping over a mountain pass, he said.
"We had a home, we had a family, we had happiness, we had prosperity, and all we have now is tears, fear and a dark future," he said, lying on a plastic sheet in a refugee camp.
Taliban militants seized much of the area under a peace deal, even after the government agreed to their main demand to impose Islamic law in the region.
U.S. officials likened the deal to a surrender. Pakistani leaders said the agreement's collapse had opened the eyes of ordinary citizens to the extremist threat.
Abbas wouldn't say how long it would take to clear the valley of 4,000 or 5,000 militants, including small numbers of foreigners - Tajiks and Uzbeks - as well as Punjabi extremists and tough Waziri fighters.
He said the military was reinforcing the 12,000 to 15,000 troops already in Swat. He gave no details, but he predicted a tough fight against militants who exploited the peace deal to regroup, descend from mountain hideouts and seize most of Swat's towns.
The troops faced guerrilla tactics, including remotely detonated homemade bombs made of explosives, steel pellets and nails packed into pressure cookers, Abbas said. Mines have been laid in Mingora.
Insurgents had forcibly recruited young boys from poor families in Swat, and sent some of them to train as suicide bombers in the South Waziristan tribal region, he said.
"We have seen with the capture of Mingora that the initiative has been taken by the militants," said Nasim Zehra, a fellow of Harvard University's Asia Center and a prominent Pakistani security analyst. "It's obviously an operation that is going to take weeks, or more."
She said strong support from Pakistan's fractious politicians and divided civil society will be vital to the army, whose previous operations have largely failed.