Thousands of Chinese paramilitary police and troops have been deployed across the Tibetan capital after hundreds of monks tried to stage a second protest in two days.

Witnesses described helmeted soldiers firing teargas yesterday to try to disperse more than 600 monks as they attempted to march out of the Sera monastery on the edge of Lhasa. The monks were forced to halt virtually at the gates of the monastery, after police at a station just outside the main entrance called in the military.

The monks, shouting “Release our people”, demanded the return of 11 monks detained on Monday after staging an anti-Chinese protest in front of the Jokhang Temple — the holiest site in Tibetan Buddhism — in the heart of the city. That protest coincided with demonstrations by about 500 monks from the sprawling Drepung monastery just outside Lhasa.

The demonstrations demanding Tibetan independence and showing support for the exiled Dalai Lama are the largest in the restive region since authorities imposed martial law after riots by anti-Chinese protesters rocked Lhasa in March 1989.

Some 600 monks from Sera refused for several hours to return to their quarters, witnesses said. It appeared that the security forces were reluctant to take more-violent measures too disperse the monks because of their large numbers and because many Tibetans living near by had gathered in a show of support for the demonstrators.

The demonstrations coincide with a series of marches around the world to commemorate the 49th anniversary on Monday of an uprising against Chinese rule in the remote Himalayan region when the Dalai Lama and many followers fled into exile in India.

Facing the ranks of soldiers and police, the monks continued to shout slogans such as, “We want human rights and freedom”, one Tibetan source said.

Clearly rattled by the bold display of opposition, Chinese authorities have ordered the closure of the north face of Mount Everest to expeditions until after the Olympic torch is carried up to its peak in early May. The expedition web portal posted a copy of a notice from the Mountaineering Association of the Tibet Autonomous Region asking climbers to delay their ascents.

The notice, dated March 10, said: “Concern over heavy climbing activities, crowded climbing routes and increasing environmental pressures will cause potential safety problems in Qomalangma [Everest] areas. We are not able to accept your expedition, so please postpone your climbing.”

The order coincides with the annual climbing season, which is in April, May and the first weeks of June.

Chinese officials had said previously that the north face of the mountain, which straddles the border between Tibet and Nepal, would remain open. They could now be concerned that international activists may try to use the occasion of the arrival of the Olympic torch to stage some kind of demonstration on the world's highest mountain. Last April, four protesters at the Everest base camp on the Tibetan side unfurled a banner reading, “One World, One Dream, Free Tibet 2008” — referring to the official games slogan. The group was deported.

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