( Reuter )- Chinese troops moved to tackle more unrest in ethnic Tibetan enclaves on Monday, as a deadline loomed for "troublemakers" who took part in protests against Chinese rule in Lhasa that some say killed up to 80 people.
Lhasa, capital of the remote, mountainous region, was under tight police watch, but reports and officials said demonstrations by ethnic Tibetans flared in at least two Chinese provinces at the weekend, piling pressure on the Communist authorities.
"We are completely capable of protecting the security of the Tibet people. Right now the overall situation in Tibet is very good," the mayor of Lhasa, Doje Cezhug, said from Beijing, in remarks posted on the Tibet government's Web site.
But protests hit ethnic Tibetan areas in the Chinese provinces of Sichuan and Gansu on Sunday, reducing the chances of an early end to the instability that is a major challenge to China's leaders just months before it hosts the Olympic Games.
In the Sichuan region of Aba, two ethnic Tibetans said hundreds of People's Liberation Army vehicles moved in overnight, after unrest in which police said a crowd of Tibetans hurled petrol bombs and set a police station and a market on fire.
"They've been driving through all night. It's just tailing off now," the man said, adding that word had spread of protests in other parts of the region as well.
In Gansu's Machu town, a crowd of 300-400 carried pictures of Tibet's exiled spiritual leader, the Dalai Lama, and shouted slogans as they marched on government buildings, breaking windows and doors and setting fire to Chinese shops and businesses, the Free Tibet Campaign said.
The London-based group said 100 Tibetan students staged a sit-in at Northwest Minority University in Gansu's capital, Lanzhou, a worry for a country with a history of student unrest, notably the Tiananmen Square protests of 1989 that ended in a bloody military crackdown.
In Lhasa, the situation was quiet but tense, with a heavy police presence ahead of a Monday midnight deadline that Tibet's government set for protesters to give themselves up to the police.
Otherwise, they would be "sternly punished," the region's judicial authorities warned.
The government advised foreign tourists to leave and confirmed it had stopped granting foreigners tourist permits.
"If the Tibetans in Lhasa take to the streets again in large numbers and really challenge the Chinese authorities, I think we'll see a very harsh crackdown," said Kenneth Lieberthal, a political scientist at University of Michigan.
The Tibetan Centre for Human Rights and Democracy, a non-governmental group in the Dalai Lama's base of Dharamsala, said security forces has already begun house-by-house raids.
Western governments have called for restraint in China's response to the violent protests, and Chinese official media tried to defend the security measures used in quelling them.
"Throughout the incident, Lhasa police officers exercised great restraint. They remained patient, professional and were instructed not to use force," Xinhua news agency said.
China's rulers brook no challenge to their rule, and the unrest comes at a time of growing threats to social stability fuelled by inflation and a yawning gap between rich and poor.
The Dalai Lama, who has lived in India since 1959, the year of a failed uprising against Chinese rule in Tibet, called for an investigation into what he called cultural genocide. Communist troops entered Tibet in 1950, after taking power in Beijing.
A Nobel peace prize winner, the Dalai Lama is revered in the Tibetan community but reviled as a traitor in China, where authorities stepped up the rhetoric against him.
Xinhua quoted Tibetan officials as saying the Dalai Lama's charge was "downright nonsense" and trumpeted its development policies in the region.
Critics say those policies helped fuel the protesters' anger by favoring Han Chinese migration to the region, contributing to a huge wealth gap between Chinese and Tibetans.