<< Monks take part in a peace march in Dharamsala, India, part of worldwide protests to mark the 49th anniversary of the Tibetan uprising. (Manan Vatsyayana/AFP/Getty Images)

More than 1,000 armed police and security personnel surrounded an estimated 500 to 600 monks from the Sera monastery Tuesday as they marched near a police station, and police fired tear gas into the crowd, one witness told the RFA's Tibetan service.

"There were probably a couple of thousand armed police, (public security bureau) personnel, wearing different uniforms. Police fired tear gas into the crowd," the unidentified witness said.

It was difficult to get independent corroboration of the event.

A woman who answered the phone at the public security bureau in Lhasa denied knowledge of the incident. At the local government office, a man who identified himself as Bianba said he was aware that an incident took place Tuesday, but would not give further details.

The latest incident came a day after Buddhist monks staged two major protests in a bold, public challenge to China's rule, using the anniversary of a failed Tibetan uprising against Beijing rule in 1959.

Several hundred monks from the Drepung monastery began their march Monday afternoon, splitting into three groups heading in different directions, an eyewitness monk told the Free Tibet Campaign, another advocacy group.

One group shouted "Free Tibet" as they walked until they were broken up at a checkpoint and dragged away from each other by police, he said. Some of the monks were arrested while those who were not returned to the monastery around midnight, he said.

RFA also reported gunshots were heard overnight from the direction of the monastery, which remains blocked off by police.

Champa Phuntsok, the head of the Tibetan regional government, confirmed Tuesday authorities briefly detained some monks from Drepung monastery, but said they were released shortly afterward after being questioned and "counseled."

Radio Free Asia and phayul.com Web site, which is run by Tibetan exiles, said as many as 71 people, mostly monks, were detained following the Monday protests.

Foreign Ministry spokesman Qin Gang also confirmed Tuesday there had been protests. "Some ignorant monks in Lhasa abetted by a small handful of people did some illegal things that can challenge the social stability," he told a news conference.

Monks in two more monasteries in northwestern Qinghai province — the Lutsang monastery and Ditsa monastery — also staged protests on Monday, RFA said, quoting "sources." Police surrounded the Ditsa monastery during the protest but did not intervene or detain anyone.

The protests in Tibet came as several hundred Tibetan exiles defied police orders against a march to Tibet from Dharmsala, India, where their spiritual leader, the Dalai Lama, has presided over a government-in-exile since the abortive 1959 uprising.

The march aimed to protest the Beijing Olympics. Indian police said it violated an agreement between New Delhi and the Tibetan government-in-exile.

The march has not been publicly endorsed by either the exile government or the Dalai Lama, who at a separate event in India accused China of "unimaginable and gross violations of human rights" in the Himalayan region.