Some 3,000 Chinese road-builders in the remote mountains of Pakistan's Northwest Frontier Province have been surrounded by armed tribesmen seeking China's intervention to force Prime Minister Zulfiqar Ali Bhutto to resign, a highly informed Pakistan source said today.

The tribesmen, about 3,000 strong and armed, have ringed the unarmed Chinese workers in 34 camps along the so-called Silk Route the Peking government is building between the Northwest Frontier Province and China's Sinkiang Province, said the source, who has access to Pakistani army intelligence reports.

Pakistani military officials could not be reached for comment on the reports. An Asian diplomat with close contacts in the army said, however, that the reports were true. He added that the tribesmen, known as Kohistanis have had the camps surrounded for about one week.

The Kohistanis are also seeking the release of two tribal leaders who were jailed three weeks ago when they took part in a demonstration demanding Bhutto's resignation.

Both men are members of the nine-party opposition Pakistan National Assembly.

The alliance has been conducting an often-violent campaign against Bhutto since he was returned to office in national elections, March 7, Bhutto's opponents say were massively rigged.

Meanwhile retired Air Marshal Asghar Kan, probably the most popular of the nine Alliance party leaders, has called on Pakistan's armed forces leaders to disobey what he termed "illegal" order to fight demonstrators. Asghar made his appeal in a letter smuggled out of a police guesthouse near here, where all top Alliance leaders are being detained.

In the letter, delivered to the chiefs of staff of the three branches of the armed forces and to 3,000 officers, Asghar charged that Bhutto "has violated the constitution and is guilty of a grave crime against the people," adding:

"It is not your duty to support his illegal regime nor can you be called upon to kill your own people so that he can continue in office a little longer. Let it not be said that the Pakistan armed forces are a degenerate police force fit only for killing unarmed civilians."

About 3,000 people have been killed since the elections."

A foreign observer noted that since the National Assembly approved legislation providing the armed forces and the civilian government with extraordinary powers to combat the current agitation last week. Asghar's appeal could be considered treasonous.

The Kohistani tribesmen, who are among the most zealous Moslems and ferocious fighters in Pakistan, are understood to have released a small delegation of the surrounded Chinese workers so they could contact their government.

Whether the Pakistani army will try to move against the tribesmen is not yet clear. The high-attitude terrain is particularly difficult, and a military source said it would take infantrymen about 10 days to reach the surrounded camps. As of today, the camps were said to have just one day's rations left.

The army would also have to consider the dancer that reprisals against the Kohistanis could enflame the entire tribal belt of half a million people, which runs through the Northwest Frontier Province and neighboring Baluchistan, which borders on Iran.

China, which has close ties to Pakistan and is a major supplier of materiel, has not commented on the campaign to oust Bhutto. The Peking government is believed to want him to remain inpower, for his opponents - mainly from stauchly Islamic parties - would probably loosen Pakistan's close links with Peking if they came to power.

An alliance spokesman said that while opposition leaders are prepared to hold discussions with Bhutto, party followers throughout the country have received orders to take to the streets again. The Alliance was frustrated in its efforts to stage a mass march on Bhutto's residence Saturday when thousands of police were moved into Rawalpindi.

The Alliance seems to have concluded that violence in the streets of the cities, which is now to be expanded to rural villages, is its main hope for forcing Bhutto out of power.

Many of Pakistan's largest labor unions support the opposition, and their strikes and slowdowns have already doubled prices of flour, tea, certain vegetables and fruits.