The Laotian government has accused China of moving troops into Lao territory to a depth of two to three miles along a six-mile front, a senior Laotian official said here today.

The director general of the Lao Foreign Office, Soubanh Srithirath, said in an interview that the Chinese incursion consisted of "several companies" and had taken place in the area north of the town of Luang Nam Tha, the southernmost point at which Chinese territory dips into Laos.

Soubanh said a note of protest was delivered to the Chinese on Saturday and the Chinese denied the charges.

That note, the latest salvo in the escalating charges of Chinese interference in Laos, also accused Chinese road builders in northern Laos of "engaging in espionage activities and laying the groundwork for a military contingency," Soubanh said.

On March 7, Laos asked China to remove its construction batallions which have been working on a 500-mile network of roads in northern Laos since 1962 under an agreement made with the former royal government of Laos.

Soubanh also said that Laos had asked the United Nations office here to remove an eight-man Chinese survey team that has been engaged in a geographic survey of Laos under U.N. auspices.

Soubanh said there were 600 Chinese in Laos, nominally workers not soldiers. "But clothes don't make the man," he said, charging that since the Chinese invaded Vietnam Feb. 17, the Chinese workers have not been engaged in road building. He said the removal order was temporary and cousultation on the projects could resume after tensions subside.

Referring to the alleged Chinese incursion into Laos, Soubanh said the Chinese had built an ammunition "warehouse" on Lao soil and "some battalions" were there to guard it. "Up to the present time we haven't conducted any military operations" against the Chinese, he said. He warned, however, that if the Chinese do not withdreaw in the near future, "perhaps we will do something."

Northern Laos is inhabited by ethnic hill tribes -- including the Meo who fought for the CIA during the Indochina war. The Communist Laotian government that came to power in 1975 still has not pacified the hills and there are reports of running battles. The Laotians fear the Chinese will arm the hill tribes against them the same way the Americans and the French did during their involvement here.

Until last July, diplomatic sources say, Laos kept a careful balance between the Chinese and the Vietnamese. Since then it has been clear that Laos would take the Vietnamese side in the confrontation with China. There are up to 50,000 Vietnamese troops in Laos Westerners estimate.

"We feel that by making a diplomatic and political approach, the Chinese will feel guilty and withdraw their troops from our land," Soubanh said. "If they do not withdraw their troop from our side, the Chinese must bear full responsibility for the consequences."

Soubanh said the Chinese actions in the north had been made without provocation. "No one in the world could believe that Lao troops would invade, fight or instigate problems with the Chinese," he said. Laos' population is about 3 million.

China has accused Laos of unilaterally tearing up the 17-year-old agreement between Laos and China on road building. The Laotian request to halt the project, China said, ran "contrary to the will of the Lao people and, therefore, is very repulsive," according to Chinese radio broadcasts.

The propaganda battle over Laos was launched March 2 when the Soviet Union accused the Chinese of massing troops on the Lao border. The change was picked up by the Vietnamese and Laotians. Soubanh said the Chinese had "more than two divisons" on the Lao frontier and he considered more than one battalion to be a threat to Laos.

On March 6 the Laotians also accused the Chinese of sending spies into Laos "to create divisons among the Lao people of ethnic nationalities..."

Why Laos would see a quarrel with the Chinese as in its interest has puzzled foreign diplomats here. The Laotians say they are worried that China will attack Vietnam through Laos.

Another explanation may be, that the 17-year Chinese presence in northern Laos became intolerable to the Vietnamese and their Soviet allies once China had shifted from a propaganda war to a shooting war against Vietnam.

It may be the potential threat to Vietnam's western flank that concerns the Vietnamese and the Laotians are simply responding to Vietnamese and Soviet pressure to get the Chinese out. The talk about the Chinese buildup on the border could be an excuse to ask the Chinese to give up the road project.