Fierce Moslem tribesmen surrounding thousands of Chinese road workers are threating to kill them because the Chinese Government has not met an "ultimatum" to force the resignation of Pakistan's Prime Minister Zulfigar Ali Bhutto, a traveler reaching here tonight said.

The traveler who reported thousands of heavily armed Pakistan troops moving up the mountainous Karakorum Highway to where the workers are reportedly being held hostage, said he had been told of the "ultimatum" by a fjailed leader of the Kohistani tribesmen.

The ultimatum for Chinese intervention in the tense political confrontation Bhutto and the nine-party opposition Pakistan National Alliance expired today, and "Now we will start killing them" - the road workers - the traveler quoted tribal leaders Faqir Mohammed as saying.

At the same time, the Pakistani Government, which up to now has denied any knowledge of hostile activity on the highway, said a soldier and five other people had been killed in fighting between troops and "certain elements" at the town of Dubair along the road.

The Chinese government has not made any public statement on the situation, but the Chinese ambassador in Islamabad, Pakistan's capital, is known to have met with Bhutto earlier this week. The question of Chinese pressure and possible intervention to free the road workers undoubtedly has added to Bhutto's problems.

Because the region is so remote, no word of the situation has been published in Pakistan's controlled press. However, several Western news reports earlier this week on the situation have begun to filter into Pakistan and this may be why the Bhutto government issued its statement.

The statement made no mention of any Chinese workers surrounded by Kohistanis, and an Information Department official termed earlier foreign press reports on the matter "completely baseless and wrong."

The traveler who met the tribal leader is a Pakistani with close military connections and openly sympathetic to the opposition Alliance, which is trying to drive Bhutto out because he allegedly rigged the March 7 national elections.

The tribal leader told the traveler at Haripur central jail, where he is being held with 2,000 other political prisoners, that 100,000 tribesmen armed with rifles and surrounded 7,000 Chinese workers and 7,000 Pakistani engineers and laborers in 34 camps along the 493-mile highway. They are building between China's Sinkiang Province and Pakistan's Northwest Frontier Province.

But knowledgeable sources in Rawalpindi said they believe that no more than 10,000 tribesmen, 3,000 Chinese and a smaller number of Pakistani road workers are involved. Altogether some 40,000 Chinese are believed to be working on the highway.

The hostage road workers are said to be strung out along a 90-mile stretch of highway between a fort at Besham and the town of Basha, 120 to 150 miles from the Sinkiang border at an altitude of 17,000 to 20,000 feet.

A military source in Rawalpindi said it would take infantrymen about 10 days to reach the beleaguered camps.

The traveler said the elderly, white-bearded Faqir told him he had been brought to Rawalpindi last Wednesday night to meet with Tikka Khan, the minister of state for defense.

Faqir said Tikka told him that the Chinese government had informed Pakistan that it was alarmed about the situation and "did not want to see any dead bodies" among is workmen.

Tikka, a retired Army Chief of Staff, reportedly asked Faqir to go to the area and call his followers off. But the leader refused unless he was allowed to meet with the ailing president of the opposition Pakistan National Alliance, Maulana Mufi Mahmud, Bhutto, however, told Tikka no such meeting would be allowed and ordered Faqir back to jail.

Faqir reportedly told the traveler that the tribesmen had no animosity toward the Chinese workers but would have no compunction about killing them to force China to intervene to get Bhutto out.

The traveler said he drove along the highway from Abbotabad to Dhodial, 45 miles apart, before driving back to Rawalpindi and saw 1,000 troops, 100 jeeps and 100 civilian trucks fitted with Pakistani manufactured machine-guns on improvised bipods. Some vehicles were towing 105-mm howitzer, capable of being broken down and hauled by mules over the rugged terrain to the Chinese work camps.

He heard two Pakistan Air Force ground attack jet fighters pass overhead he said, and local people along the road told him the planes began making passes over the area this morning.

The traveler said he was able to identify troops and equipment from the mountain regiment of the 23d Division based at Jhelum, 68 miles southeast of Rawalpindi, and an artillery regiment of the 12th Mountain Division from Murree, 40 miles north of there. These units are specially trained to fight in rugged, high altitude terrain. He estimated that 12,000 troops in all were moving up the highway.