China deployed massive security across the Tibetan plateau on Tuesday on the sensitive 50th anniversary of a failed uprising against Chinese rule that forced the Dalai Lama into exile.
Residents of Tibet's capital, Lhasa, reported no protests on Tuesday morning but - as in other Tibetan areas of China - it appeared to be partly because armed soldiers and police were patrolling the streets in a show of force.
Peaceful protests led by Buddhist monks in Lhasa on last year's anniversary erupted four days later into anti-Chinese rioting that swept into other parts of western China with Tibetan population.
"Armed police with guns are at the intersections," a Han Chinese woman, who works at a Lhasa hotel, told AFP by telephone.
"People don't feel nervous because the police are here."
Last year's unrest deeply angered China's leaders as they prepared for the Beijing Olympics in August, and they responded with a huge military crackdown across Tibet that triggered condemnation around the world.
Signalling Beijing's lingering concern, Chinese President Hu Jintao invoked one of China's proudest nationalist symbols, the Great Wall, in a call Monday to end Tibetan separatism.
"We must build up a Great Wall in our fight against separatism and safeguard the unity of the motherland, and push Tibet's basic stability toward long-term security," he urged.
Tibetan exiles say more than 200 people died when Chinese security forces clamped down following last year's unrest. Authorities deny this, saying that "rioters" were responsible for 21 deaths.
The Dalai Lama, who embarked on a dangerous escape into India a week after the uprising on March 10, 1959, was due to address followers from his exiled base in the Indian town of Dharamashala at 0330 GMT Tuesday.
Tens of thousands of supporters have packed the town for the event, which will be broadcast on the Internet to exiles and supporters worldwide.
The 73-year-old Dalai Lama retains enormous support among the roughly six million devoutly Buddhist Tibetans who live in China, despite Chinese efforts to demonise him.
Chinese authorities say he wants independence for his Himalayan homeland. The Dalai Lama denies this, saying he wants greater autonomy for Tibetans and an end to widespread repression.
Protests have flared in Tibetan regions of western China over recent weeks despite the enormous security.
One Tibetan monk in Sichuan province set himself alight with petrol while holding an image of the Dalai Lama. Chinese state media reported that he was being treated in hospital.
China has also sought to seal Tibet and adjacent Tibetan regions of western China from independent observers and foreign reporters.
Foreign tourists are banned from visiting Tibet in March, travel agencies have told AFP, although the government insists the region remains open.
Police on Tuesday turned away AFP reporters who attempted to visit the La Jia monastery in a remote mountainous region of Qinghai province bordering Tibet.
"This is not an open place. You can't be here," a police officer said.
They were escorted from nearby La Jia town, which is about 300 kilometres (185 miles) south of the provincial capital Xining.
The reporters saw checkpoints and armed security forces on the roads.
China has ruled Tibet since 1951 after sending in troops to "liberate" the region the previous year.
Tibet's government-in-exile says tens of thousands were slaughtered in the crackdown following the 1959 uprising, with 87,000 people dying between March and October of that year alone.
In Washington, meanwhile, hundreds of Tibetan exiles gathered outside the White House and bowed their heads for a two-minute silence at 1600 GMT Monday -- midnight in the Himalayan region.
The protesters marched to the Chinese embassy and were joined by dissident Wei Jingsheng, who has questioned Beijing's historical clams to the region.
"The Tibetans have been deprived of their right to protest but we can see that they are very strong," Wei told AFP.