Pakistan admitted Tuesday that the military used intelligence from U.S.-led coalition forces in a helicopter attack that left 80 people dead, but that U.S. forces did not participate in the operation on what was described as an Al Qaeda-linked training camp.

"Intelligence sharing was definitely there, but to say they (the coalition) have carried out the operation, that is absolutely wrong," Maj. Gen. Shaukat Sultan, the chief army spokesman, said.

Sultan's clarification came after ABC News reported that a U.S. Predator drone fired into the compound after intelligence pointed to the possibility that Al Qaeda's No. 2 Ayman al-Zawahiri was present at the location.

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Another Pakistani official, speaking on the condition of anonymity, said that Zawahiri and the terror leader behind the plot to blow up trans-Atlantic airliners had frequented the religious school in Chingai village, but were not there when the attack was carried out.

The official did not say when Zawahiri or Abu Ubaidah al-Masri, the Egyptian who allegedly heads Al Qaeda's operations in eastern Afghanistan, had last visited the school.

Thousands of angry tribesmen decried both governments over the killings Tuesday.

Sultan said his government received intelligence as part of long-standing cooperation with the U.S.-led coalition forces in Afghanistan to battle terrorists operating along the porous border between the countries.

In Kabul, Col. Tom Collins, a U.S. military spokesman, said it is common knowledge that the United States, Pakistan and Afghanistan share intelligence as part of a three-way military agreement. But he said he had no information regarding the recent operation in Pakistan.

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Another U.S. military spokesman, Lt. Col. Paul Fitzpatrick, said the U.S. did not participate in the attack or provide the Pakistanis with any forces, aircraft or equipment. He declined to say, however, if other American assistance was provided.

"Pakistan is a U.S. ally in the war on terror and the United States does routinely share intelligence with its allies, however, I cannot comment on any particular operation," he said.

As many as 20,000 people protested Tuesday in Khar, the main town in Pakistan's northwestern tribal Bajur district, claiming innocent students and teachers were killed in the attack. They chanted: "God is Great!" "Death to Bush! Death to Musharraf!" and "Anyone who is a friend of America is a traitor!"

"We will continue our jihad (holy war)! We will take revenge for the blood of our martyrs!" a local Islamic cleric, Maulana Roohul Amin, yelled into a loudspeaker at the rally. "The forces of infidelity are trying to erase us from existence!"

In the northwestern city of Peshawar, 500 members of a hard-line Islamic group burned an effigy of President Bush and denounced Pakistani President Gen. Pervez Musharraf. A smaller protest was also held in the southern city of Multan.

Islamic leaders had called for nationwide protests Tuesday to denounce the raid in Chingai village, about 6 miles from Khar near the Afghan border. It was the deadliest military operation known to have been launched against suspected militants in the country.

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Pakistan said its helicopters fired five missiles into the madrassa, flattening the building and killing 80 people inside. Three men survived with serious injuries.

The attack threatened efforts by Musharraf to persuade deeply conservative tribespeople to back his government's efforts against pro-Taliban and Al Qaeda fighters, who enjoy strong support in many semiautonomous regions in northern Pakistan.

It also sparked claims of U.S. collusion with Pakistan, with villagers saying fixed-wing drone aircraft were seen flying over the town in the days before the attack, according to the Dawn daily newspaper.

In January, a U.S. Predator drone fired a missile targeting Zawahiri in Damadola, near Chingai. The strike missed Zawahri, but killed several other Al Qaeda members and civilians and sparked massive anti-U.S. protests across Pakistan.

Fears were high that Monday's attack will fan unrest across Pakistan, which also witnessed violent protests this year after European newspapers published cartoons of Islam's Prophet Muhammad, and after the August killing of a ethnic-Baluch tribal chief in another Pakistani military raid.

Scores of pro-government tribal police deployed throughout Bajur on Tuesday and blocked roads with stones to prevent political activists and journalists reaching Khar and Chingai, a local government official said on condition of anonymity as he was unauthorized to speak to the media.

Small protests were held in several Pakistani cities, including Peshawar, Karachi and Multan on Monday. The unrest caused Britain's Prince Charles, currently in Pakistan, to cancel his planned Tuesday trip to Peshawar in the country's northwest.

Many local lawmakers and regional Cabinet ministers resigned in protest over the attack. The planned signing of a peace deal between tribal leaders and the military was also canceled Monday in response to the airstrike.

"Islamabad is acting against its own citizens who profess loyalty, promise to maintain peace and to ... eliminate foreign militants," a Pakistan daily, The Nation, said in an editorial.

Ali Dayan Hasan, a South Asia representative for Human Rights Watch, accused Pakistani authorities of "persistent use of excessive and disproportionate force ... in pursuing counter-terror operations."

Among those killed Monday was Liaquat Hussain, a fugitive cleric and Zawahiri associate who ran the targeted madrassa. The raid was launched after Hussain rejected government warnings to stop using the school as a terrorist training camp, the military said.

Another Zawahiri lieutenant, Faqir Mohammed, left the madrassa 30 minutes before the strike, according to a Bajur intelligence official who spoke on condition of anonymity as he was not authorized to speak to the media.

Pakistan's most influential Islamist political leader, Qazi Hussain Ahmed, was to lead a convoy of cars Tuesday from the northwestern city of Peshawar to Khar and Chingai, his spokesman, Shahid Shamsi, said.

"They killed 80 teenagers who were students of the Quran," Ahmed told reporters on Monday. "This is a very cruel joint activity (between the U.S. and Musharraf governments)."

The Associated Press contributed to this report.