ISLAMABAD, Pakistan - Taliban extremists ambushed a convoy of vehicles carrying at least 400 students, staff, and relatives from a boys' school yesterday, taking dozens - possibly hundreds - captive in northwestern Pakistan, officials said.

The army said today that its troops had rescued 79 of the captives, with at least one person still missing.

The brazen abduction was part of a string of extremist actions in Pakistan's tribal belt that the army believes is partly aimed at distracting the military from its offensive against the Taliban in the Swat Valley. The extremists were said to have rockets, grenades, and automatic weapons.

Details were still emerging early today about what exactly happened in North Waziristan. Originally, as many as 500 people were believed to have been abducted, but about 200 students were later found to be safe. Army Maj. Gen. Athar Abbas said a group of 80 had been held in North Waziristan's Goryam area.

The kidnapping raised the possiblity that the boys could have been used as human shields. Many of the boys at the college are children of army officers, making them even more valuable. The development came as Richard Holbrooke, the U.S. special envoy to the region, is scheduled to arrive in Pakistan tomorrow.

Police official Meer Sardar said the abductions occurred about 20 miles from Razmak Cadet College. The victims were leaving the school area after they were warned to get out in a phone call from a man they believed to be a political official, Sardar said, citing accounts from a group of 17 who managed to escape.

Local media, however, reported the group was leaving because school vacation had started.

About 30 buses, cars, and other vehicles were carrying the students, staff, and others when they were stopped along the road by a large group of gunmen in their own vehicles, according to a school employee who escaped.

The employee requested anonymity out of fear of Taliban reprisal and said the school's principal was among those abducted. The staffer said the assailants carried rockets, Kalashnikovs, hand grenades, and other weapons. He estimated 400 captives were initially involved.

Police were negotiating with the Taliban via tribal elders for the hostages' release, said Mirza Mohammad Jihadi, an adviser to the prime minister. He said the hostages were being held in the Bakka Khel area.

About midnight, Javed Alam, a school vice principal, said about 200 of the students who had apparently evaded capture were tracked down at their homes. The principal was missing.

Students made up the majority of the group. Cadet colleges in Pakistan are usually run by retired military officers and educate teenagers. They also typically provide room and board.

North and South Waziristan are major al-Qaeda and Taliban strongholds bordering Afghanistan. They lie roughly 150 miles from the Swat Valley. Clashes in the last three days in South Waziristan have killed at least 25 extremists and nine soldiers. In the latest attack, reported by the army yesterday, extremists fired rockets at troops, killing two.

The fresh fighting is fueling speculation that a month after reigniting its battle against Taliban fighters in Swat, the military will widen the offensive to South Waziristan. But the army spokesman, Abbas, said that for now, troops on the ground were simply reacting to attacks, not opening a new front.

With the military's hands full in Swat, opening a front in South Waziristan now would be risky for the army.

Known for its harsh terrain, reticent tribes, and porous border with Afghanistan, as well as its history of limited federal government oversight, South Waziristan would likely be a tougher test for Pakistan's armed forces than Swat. The region also is the main base for Pakistani Taliban chief Baitullah Mehsud.