Islamabad, Pakisan ? Pakistan’s military defended its deadly missile strike on an Islamic school, saying Wednesday it was necessary to prevent terrorist trainees from escaping. Critics said the government used disproportionate force in the attack, which killed 80 people.

Tribal elders said Monday’s raid in the Bajur district near the Afghan border set back peace efforts in Pakistan’s northwestern tribal region, and a prominent human rights group demanded an independent inquiry.

Abdul Aziz Khan, head of Bajur’s council of tribal chiefs, demanded a guarantee there would be no further attacks, saying, “without it we will not begin talks with the government.” At stake is a deal to stamp out militancy like that reached in September with tribal chiefs in North Waziristan.

Protests erupted for a third day in Bajur, with 10,000 tribesmen – including masked militants linked to al-Qaida – demanding the deaths of Pakistani President Gen. Pervez Musharraf and President Bush.

Musharraf’s government has been roundly condemned in Pakistan for the attack on the school in the village of Chingai, two miles from the poorly demarcated border separating Pakistan from Afghanistan’s Kunar province, where U.S. troops have repeatedly battled al-Qaida militants.

Tribespeople and Islamic leaders denounced the raid as an illegitimate attack on innocent students and teachers and threatened retaliation.

Many people blamed the U.S. military for carrying out or providing intelligence for the attack. Residents reported seeing unmanned drone surveillance aircraft flying over the town. Pakistani officials denied U.S. involvement and said they had aircraft – provided by the Americans – capable of carrying out surveillance.

Pakistan’s chief army spokesman, Maj. Gen. Shaukat Sultan, said the military had no option but to use helicopter gunships against the school, which he said was a front for a militant training camp, because attempts to arrest suspected trainee terrorists could have led to their escape.

“The biggest factor that contributes to success is surprise,” Sultan told The Associated Press. “If we lost the surprise by 10 minutes, the operation (was) likely to fail.”

Sultan said evidence included students in their 20s seen conducting exercises outside the school, school leaders who told rallies they were preparing suicide bombers and other intelligence he declined to specify.