The Communist Party boss of Tibet said the region is stable following anti-government riots last month, but warned of possible plots to sabotage the Olympic torch relay, state media reported Sunday.

Tensions have been simmering in the Tibetan capital and nearby provinces since before the anti-Beijing protests exploded into violence.

Chinese authorities say 22 people died in Lhasa on March 14, but the Tibetan government-in-exile says up to 140 were killed in the riots and the government's ensuing crackdown.

The protests in the Himalayan region have focused increased international scrutiny and criticism on China in the run-up to this summer's Olympic Games.

China plans to take the Olympic torch to Tibet twice. One torch will be taken up Mount Everest, the world's tallest peak, in early May, while the regular torch will pass through Lhasa in June.

"The social order in Lhasa and other parts of Tibet" has returned to "normal," the official Xinhua News Agency quoted Tibet's Communist Party boss, Zhang Qingli, as saying.

But he warned "that grave challenges remain ahead, as the Dalai clique is plotting for new sabotage activities."

Authorities had "to spare no efforts in preparing for the torch relay to ward off any possible mishap," Zhang said, providing no other details.

Beijing has repeatedly accused the Dalai Lama and his supporters of orchestrating the recent violence -- the longest and most sustained challenge to China's 57-year rule in the Tibetan region.

It is a charge the spiritual leader has repeatedly denied.

China says it has ruled Tibet for centuries, although many Tibetans say their homeland was essentially an independent state for most of that time. Chinese communist troops occupied Tibet in 1951 and Beijing continues to rule the region with a heavy hand.

Taking the Olympic torch to the top of Everest is seen by some as a way for Beijing to underscore its claims to Tibet, and has drawn criticism from Tibetan activist groups.

The torch relay has become a rallying point for a wide range of groups angry at China, and protests were expected when it is taken through London on Sunday. Demonstrations are also expected Monday when it is in Paris and Wednesday when it makes its only North American stop in San Francisco.

China has imposed a security clampdown on Tibetan areas in the western part of the country in an effort to rein in the anti-government riots and protests.

In the latest reported violence, the London-based Free Tibet Campaign and the International Campaign for Tibet said that eight people were killed Thursday when police or paramilitary police opened fire on a protest in Garze Tibetan Autonomous Prefecture in Sichuan province.

State media reported that one government official was seriously injured in what it described as a riot.