KHWAZAKHELA, Pakistan -- Pakistani security forces, after seizing a key militant training camp in the Swat Valley, were pressing toward the main town held by the Taliban as a senior military officer said the government's goal is to eliminate the militants' entire leadership.

The Taliban have dug in for a long fight with aid from allies in neighboring Afghanistan, according to a letter shown to reporters in Swat by military officials. The letter appeared to be a pledge of moral and financial support by Mullah Omar, the supreme commander of the Afghan Taliban militia. "The hardcore militants would never surrender," Maj. Gen. Sajjad Ghani, commander of Pakistani troops in northern Swat said on Friday. "We have to eliminate them."

Since the collapse of a peace deal a few weeks ago that had given the Taliban control of the scenic valley north of Islamabad, the militants and Pakistani troops have been engaged in fierce fighting that has caused a massive refugee crisis, forcing about two million people to flee their homes.

On Friday, the United Nations issued a flash appeal for a total of $543 million in humanitarian aid to help the refugees. Martin Mogwanja, acting U.N. humanitarian coordinator, said: "The scale of this displacement is extraordinary in terms of size and speed and has caused incredible suffering."

In the latest government victory, Pakistani security forces seized a key militant training camp Wednesday on a 7,000-foot high mountain ridge less than 14 miles from the main town of Mingora, giving government forces control of a strategic point. The camp, Binya Baba Ziarat, was captured after two weeks of intense fighting, officials said. A maze of caves and underground bunkers provided shelter to the militants against attack by government forces. "It was very hard to dislodge the militants from that position," said Gen. Ghani said.

Up to 150 militants were killed in the battle, described by the military officials as the bloodiest since Pakistani troops launched the recent Swat offensive. "Some 100 bodies are probably still buried inside one" of the caves, said Col. Mohamed Riaz, who led the final charge.

The camp was used by the Taliban as a center for training young men who were forcibly recruited, officials said. Mohamed Akhtar, a 14-year-old schoolboy, said he was rescued by the security forces. He was taken to the camp some five months ago to be trained as a suicide bomber, he said. "There were dozens of young boys in the camp," he said. "At least three of my colleagues became suicide bombers."

Around 15,000 troops are engaged in the fighting in Swat. They have also seized control of two major towns in northern Swat, Matta and Khwazakhela. Despite the advances, "We cannot give any timeline for the end of fighting," said Gen. Ghani. Some senior militant commanders have been killed in the recent fighting but the top leadership has survived, officials said.

The Taliban in Pakistan is led by Mullah Fazalullah, a young radical cleric who is being supported by other militants operating in Pakistan's lawless tribal areas. Pakistani military officials said a large number of foreign fighters including Arabs, Afghans and Uzbeks have joined the fighting in Swat.

Gen. Ghani said villagers have started taking up arms against the Taliban in several areas, indicating growing confidence in the military operation. "The people have started forming armed groups to fight the Taliban," he said.