LHASA, TIBET, OCT. 8 -- Tibetan authorities ordered foreign reporters out of Tibet today and maintained a tight security clampdown on its troubled capital after anti-Chinese violence erupted in the Himalayan region.

Yu Wuzhen, director of Tibet's foreign affairs office, met with 15 foreign reporters at midnight last night in Lhasa and ordered them to leave within 48 hours or "face the consequences."

{In Washington, State Department spokesman Charles Redman said the United States regrets "that the Chinese have taken this action to restrict the free flow of information about a topic of worldwide interest."}

Two U.S. diplomats present at the meeting were to meet Yu today to discuss the expulsion. A U.S. Embassy spokesman in Beijing said it was not known if the diplomats would also have to leave.

A source close to the Tibetan government, meanwhile, said police had released after a few hours' detention 80 monks taken into custody Tuesday during a protest march that was broken up by baton-wielding police. The protesters were freed "because they did not use violence," the source said.

But there were also reports that police had conducted sweeps at several monasteries and arrested other monks. The Buddhist clergy, who once held sway in Tibet, has been in the forefront of protests demanding independence from China.

Although many shops and markets were closed in the Tibetan capital, no fresh protests were observed after security was tightened yesterday on the anniversary of the 1950 Chinese invasion of the one-time theocratic state, many of whose 1.5 million inhabitants have never accepted Beijing's rule.

Police manned roadblocks on routes to Lhasa's three biggest monasteries, and officers searched all vehicles entering and leaving the city. The official New China News Agency said "everything has returned to normal" in Lhasa.

Telex and telephone lines to Lhasa were not working for a second day following nearly two weeks of anti-Chinese protests. In the second demonstration on Oct. 1, witnesses said, police opened fire on protesters. At least six persons died.

This dispatch was sent with a traveler to Chengdu, the nearest major Chinese city.

In a move seen as signaling official concern, Yu said the American, British, French, Italian, Canadian and Australian reporters had violated rarely enforced Chinese government rules requiring them to apply in advance to travel to Tibet.

Yu said the reporters had engaged in "illegal" activities by covering the demonstrations, which began Sept. 27.