Islamabad, Pakistan -- A former Guantanamo prisoner thought to have forged ties with al-Qaida since his release is leading a militant band whose members have strapped explosives on two Chinese engineers they kidnapped in a lawless region near the Afghanistan border.

With Pakistani security forces deployed in the mountainous tribal area where the kidnappers were holed up, local leaders sought Tuesday to negotiate the release of the two Chinese, who were building a dam when they were kidnapped Saturday.

The five kidnappers threatened to kill the hostages unless the militants are allowed safe passage to a nearby area where their one-legged leader, Abdullah Mehsud, is believed hiding, officials said.

Mehsud, 28, came back to Pakistan in March after about two years' detention at the U.S. Navy base at Guantanamo Bay, Cuba. It was not clear why U.S. authorities released Mehsud.