A former prisoner at the U.S. Navy facility at Guantanamo Bay, Cuba, thought to have forged ties with al Qaeda since his release, is leading a militant band whose members kidnapped two Chinese engineers in a lawless region of Pakistan near the Afghan border, officials said.

With Pakistani security forces deployed in the mountainous tribal area where the kidnappers are holed up, local leaders sought Tuesday to negotiate the release of the two Chinese, who were kidnapped Saturday. Both are engineers who were helping Pakistan build a dam.

The five kidnappers have strapped explosives to the hostages and threatened to kill them unless the militants are allowed safe passage to a nearby area where their leader, Abdullah Mehsud, is believed to be hiding, officials said.

"We will not accept this demand," Brig. Mahmood Shah, chief of security for Pakistan's northwestern tribal regions, said in a telephone interview. Shah said troops surrounded the kidnappers but were refraining from the use of force for the safety of the hostages.

Mehsud, 28, came to Pakistan in March after about two years of detention at Guantanamo Bay. He was captured by U.S.-allied Afghan forces in Kunduz in northern Afghanistan in December 2001 while fighting for the Taliban, Pakistani officials said.

It was not clear why U.S. authorities released Mehsud. After he returned to his tribal homeland in South Waziristan, he became a rebel leader and had opposed Pakistani forces hunting al Qaeda fighters in the semiautonomous area.

A Pakistani intelligence official, speaking on condition of anonymity, said Mehsud was believed to have recently forged ties with al Qaeda and was receiving financing from the group. Foreign militants, mainly from Uzbekistan, are loyal to Mehsud, the official said.

At least one other former Guantanamo detainee returned to his militant past. Abdul Ghaffar, an Afghan who fought for the Taliban, was released in 2002 after eight months in detention to become a commander for the Islamic militia in southern Afghanistan. He was killed by U.S. forces in a gun battle last month.

Pakistan's military has staged a series of offensives this year targeting al Qaeda fighters in South Waziristan and claims to have broken up several hideouts and training camps. Dozens of guerrillas, soldiers and civilians have been killed in the fighting.

The remote region is also a suspected hiding place of Osama bin Laden, the al Qaeda leader, and his top lieutenant, Ayman Zawahiri, although there is no firm evidence on their whereabouts.

Pakistani tribal elders meet to discuss the release of two Chinese engineers. Abdullah Mehsud was in U.S. detention at Guantanamo Bay for about two years.