BEIJING, OCT. 31 -- Three high-level government and Communist Party officials from Tibet said today that the Chinese government has "definite evidence" that the Dalai Lama, the exiled Tibetan Buddhist leader, and his "clique" had planned and instigated the anti-Chinese rioting that erupted in Lhasa, the Tibetan capital, a month ago.

At a news conference here, the first held by leading Tibetan officials since rioting broke out Oct. 1, the Tibetans denied reports of widespread arrests in Lhasa and declared that the city is quiet and open to foreign visitors.

The Communist Party secretary of Lhasa, Goigya, said six persons were killed in the Oct. 1 riot, but only about 100 persons were active participants in the disorder. He said 10,000 persons were at the scene during the rioting, but they were only on-lookers. According to reports at the time, hundreds of persons were involved in the rioting.

At the news conference, which was held under the auspices of an eight-day Communist Party congress, the three officials, all Tibetans, defended the Chinese government's policies and performance in Tibet. The congress ends Sunday.

The deputy Communist Party secretary of Tibet, Danzim, said, "We have definite evidence that the unrest was caused as a result of the instigating and plotting of the Dalai Lama clique."

The Dalai Lama has stated that the demonstrators in Lhasa may have been encouraged by a visit that he made to the United States in September. But he has not acknowledged any direct link with the demonstrators.

Doje Cering, chairman of Tibet's regional government, insisted that Tibet is now open to foreign journalists, who had been ordered to leave the region Oct. 9 after three anti-Chinese demonstrations. Several journalists here have sought to return to Tibet, but none is known to have been granted permission.

Westerners in Tibet who sympathize with Tibetans opposed to China's rule over the region sent a written report to journalists in Beijing this week saying police had made regular nighttime arrests of suspected dissidents over a two-week period after the outbreak of proindependence demonstrations in Lhasa.

The westerners' report said armed police continued to patrol Lhasa at night and that police carrying antiriot equipment made periodic shows of force during the day.

A western diplomat said today he had firm information that at least 30 Tibetans from monasteries near Lhasa were under detention.

At today's news conference, Danzim said only a small number of Tibetan Buddhist lamas had been arrested and that religious activities in monasteries near Lhasa were being conducted normally.

"Everything now in Lhasa is just the same as before the unrest occurred, and no curfew was put into practice," Doje Cering said.

A test of the Chinese government's willingness to keep Tibet open is expected soon. A diplomat said more than a dozen members of the U.S. House Armed Services Committee have asked for permission to visit Tibet during an Asian trip in late November.

It was learned tonight, meanwhile, that police in Tibet today ordered two Britons and a West German who teach English there to leave within the next few weeks. The two Britons were accused of running an illegal lending library in Lhasa. All three were charged with being illegally employed in Tibet.