ISLAMABAD, Pakistan – Pakistani helicopter gunships yesterday destroyed a religious school the military said was fronting as an al-Qaida training camp, killing 80 people in the country’s deadliest military operation targeting suspected terrorists.

Islamic leaders and al-Qaida-linked militants blamed the United States for the airstrike and called for nationwide demonstrations to condemn the attack that flattened the school – known as a madrassa – and ripped apart those inside. Furious villagers and religious leaders said the pre-dawn missile barrage killed innocent students and teachers.

U.S. and Pakistani military officials denied American involvement.

Among those killed in the attack in the remote northwestern village of Chingai, two miles from the Afghan border, was a cleric who had sheltered militants in the past and was believed associated with al-Qaida’s No. 2 leader, Ayman al-Zawahri.

The raid threatens efforts by President Gen. Pervez Musharraf to persuade deeply conservative tribespeople to back his government over pro-Taliban and al-Qaida fighters, who enjoy strong support in many semiautonomous regions in northern Pakistan. The planned signing of a peace deal between tribal leaders and the military was canceled yesterday in response to the airstrike.

Musharraf has been under intense pressure, particularly from the United States and Afghanistan, to rein in militant groups, particularly along the porous Pakistan-Afghan frontier, where Osama bin Laden and al-Zawahri are believed to be hiding. The Pakistani leader, along with Afghan President Hamid Karzai, met with President Bush in Washington last month to address the issue.

Protests were held from the northwestern city of Peshawar to the southern city of Karachi, the largest taking place in Chingai and the Bajur district’s main town of Khar, where 2,000 tribesmen and shopkeepers chanted “Death to Musharraf! Death to Bush!”

Amid fears of unrest, Britain’s Prince Charles, who arrived in Pakistan on Sunday for a five-day stay, canceled a visit planned for Tuesday to Peshawar.