Tibetan exiles are planning to demonstrate outside the Chinese Embassy in London as a deadline over unrest in the province comes into force.
Authorities in Tibet have told protesters in the autonomous region to turn themselves in by midnight local time (4pm GMT) or face "punishment".
It follows days of violence in the ancient capital of Lhasa in which 80 people have been killed, according to the Tibetan Government in Exile.
Reports suggest there have been further deaths in other towns within the autonomous region and in neighbouring Sichuan Province.
China faced increased pressure over the violence. Tibet's spiritual leader in exile, the Dalai Lama, warned of "cultural genocide" in the region.
Speaking from his base in India, he called for the province to be opened up to international observers.
The Dalai Lama said: "Whether the (Chinese) government there admits it or not, there is a problem. There is an ancient cultural heritage that is facing serious danger. Whether intentionally or unintentionally, some kind of cultural genocide is taking place."
The recent unrest in Tibet began last Monday, coinciding with the 49th anniversary of the 1959 uprising against Chinese rule.
It was initially led by Buddhist monks, but has since escalated to include large numbers of ordinary Tibetans.
Human rights watchers fear that the crackdown against protesters by security forces could turn increasingly bloody.
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