Thousands of Chinese security personnel fired tear gas to try to disperse more than 600 monks taking part in a second day of rare street protests in Tibet, a source and Radio Free Asia said on Wednesday.
The Tibet demonstrations follow a string of marches around the world to commemorate the 49th anniversary of an uprising against Chinese rule in the remote, mountainous region that has become a flashpoint for protesters ahead of the Beijing Olympics.
"The police were armed with electric prods. Other uniformed security forces had firearms," the source told Reuters, requesting anonymity.
"The monks chanted: 'Release our people'," the source said, quoting a witness. The group, from the Sera Monastery, also shouted "We want human rights and freedom", the source said.
On Monday, 300 monks defied authorities by staging a march in the Tibetan capital of Lhasa, which a Chinese Foreign Ministry spokesman described as "an illegal activity that threatened social stability".
Chinese troops invaded Tibet in 1950 and nine years later the Dalai Lama, the spiritual leader of Tibetan Buddhism, fled into exile after a failed revolt against Chinese rule.
Tibet has since become a point of contention between Chinese Communist leaders and those who advocate independence or greater autonomy for the region.
Radio Free Asia said the monks from the Sera Monastery were demanding the release of fellow monks detained for protesting a day earlier.
About a dozen monks from Sera were detained earlier this month for waving a Tibetan flag and shouting pro-independence slogans, the source said, adding that government officials said they had been rounded up for "very serious" crimes.
The pro-Tibet protests around the world in the last week and the demonstrations within the heavily policed region itself are precisely what China's Communist rulers are keen to avoid ahead of the Olympics in August.
Foreign Minister Yang Jiechi told unwelcome critics to back off on Wednesday, accusing them of violating the Olympic Games charter keeping politics away from sports.
"More and more countries ... have recognised that this issue concerns China's sovereignty and territorial integrity. It is not a religious or ethnic issue," Yang told a news conference.
On Wednesday, reports said China had closed the north face of Mount Everest to expeditions until after the Olympic torch ascends its peak in early May.
The Expedition Web portal www.mounteverest.net carried a notice on its site from the Mountaineering Association of Tibet Autonomous Region of the People's Republic of China asking climbers to postpone their ascents until after May 10.
"Concern over heavy climbing activities, crowded climbing routes and increasing environmental pressures will cause potential safety problems in Qomalangma areas," said the notice, dated March 10. "We are not able to accept your expedition, so please postpone your climbing project until after May 10."
Everest, where five Americans unfurled "Free Tibet" banners last year, is known in China by its Tibetan name, Qomalangma.
India, whose hill station town of Dharamsala is home to Tibet's government-in-exile and the Dalai Lama, also saw a spurt of activity over the issue of who rules the Buddhist region.
In New Delhi, about 40 Tibetan nuns tried to storm the Chinese embassy, but were turned back and detained by Indian police, who briefly used water cannon on the protesters.
Around 500 Tibetan women also marched peacefully through the streets of Dharamsala, activists said.
And around 100 marchers, including monks, nuns and young people born in exile, set off on the third day of their march from Dharamsala to Tibet, closely watched by Indian police and officials who hope to keep them within the district of Kangra.
(Additional reporting by Desmond Boylan in New Delhi)