Buddhist monks and Tibetan nationals battled police and burned cars and shops as the worst violence to break out in that occupied country since the late 1980's threatened to throw a monkey wrench into the Chinese government's Olympic plans:

The chaotic scene was the latest, and most violent, confrontation in a series of protests that began on Monday and now represent a major challenge to the ruling Communist Party as it prepares to play host to the Olympic Games in August.

By Saturday morning, Chinese armored vehicles were reportedly patrolling the center of the city. Beijing is facing the most serious and prolonged demonstrations in Tibet since the late 1980s, when it suppressed a rebellion there with lethal force that left scores, and possibly hundreds, of ethnic Tibetans dead.

The leadership is clearly alarmed that a wave of negative publicity could disrupt its elaborate plans for the Olympics and its hopes that the games will showcase its rising influence and prosperity rather than domestic turmoil.

Thousands of Buddhists in neighboring India and Nepal took to the streets Friday in solidarity. Concerned that the protests might spread elsewhere in China, the authorities appeared to be moving the military police into other regions with large Tibetan populations.

China's top official in Tibet, a vast region formally annexed by the country in 1951, said the protests were part of a "separatist" movement led by exiled spiritual leader the Dalai Lama that authorities would not allow to succeed.

"The plot of the separatists will fail. We will challenge them firmly, according to law," the chairman of the Tibet government, Qiangba Puncog, told reporters in Beijing on the sidelines of China's annual parliamentary session. "This is very clear: This is a separatist Dalai Lama clique, inside and outside the country."

Authorities warned that those involved in the riots should turn themselves in by midnight on Monday.

"Violators who do not comply with the deadline will be severely punished under the law," said a joint notice issued by the Tibetan police and judicial authorities.