Pakistani troops with tanks have moved in strength into the Khyber Tribal Agency area bordering Afghanistan, in a crackdown on dissident tribesmen who have been getting guns from Kabul.

After a gradual buildup of security forces over the past two weeks, the Khyber was sealed off Monday and telephones were cut off.

Khalid Aziaz, the commissioner of Peshawar division, ordered 16 tribal leaders to surrender to the Khyber political agent -- the government's local administrator. If they did not, the government said, it would consider itself free to take whatever action it saw fit, including the destruction of their homes -- a traditional punishment and one that was meted out last March to dissident leader Wali Khan Kuki Khel in an earlier attempt to scare him off.

Two of the wanted men surrendered. The surrender of another was promised by his family. The rest, it is believed, took refuge deep in the hills, where most of the Khyber's 600,000 Afridis live and where the government traditionally does not penetrate.

The chief of Malik, Nader Khan, whom the government has been trying to build up as a rival to Wali Khan, said that the destruction with heavy weapons of selected dissidents' houses had already begun.

Aziaz warned the tribes in general to have nothing to do with "these subversive elements" whom he described as "communist agents, anti-Islamic and anti-Pakistan."

He threatened that if government forces were fired on or obstructed they would respond. They would be at liberty to go anywhere, even into the areas traditionally outside government control, he said, and stay there as long as they liked until it was considered that the local tribe was able itself to "clean out subversives." Nader Khan said those who had surrendered would probably be released after a month or so, if they promised not to have anything more to do with Wali Khan or Kabul.

The seeds of this tribal unrest are complex. Heroin is involved: the government claims that the dissidents are also heroin smugglers but independent observers consider there to be widespread involvement in and outside the agency, as well as official corruption.

Wali Khan scorns negotiation with the authorities on the grounds that "they do not represent the people," and admits to receiving aid from Kabul -- in the form of guns, which are currency in the tribal areas.

The government crackdown may further damage Pakistan's relations with its independent tribes, which are administered, as they were under British rule, by a political agent armed with wide powers of patronage.