Tibetan activists are making last-minute preparations for rallies marking the failed 1959 Tibetan uprising against Chinese rule.
Rights groups plan to demonstrate Wednesday outside the United Nations in New York, and at the Chinese embassies in Washington, London, Italy, Sweden and Paris.
March 10 is the 51st anniversary of the uprising that sent Tibet's spiritual leader, the Dalai Lama, into exile in India. It also marks the second anniversary of deadly riots that swept the Tibetan capital, Lhasa.
The Dalai Lama will make a special address Wednesday from Dharamsala, India, the home of Tibet's exiled government.
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In New Delhi Tuesday, Tibetan activists tried unsuccessfully to enter the Chinese embassy. Indian police detained nearly two dozen protesters before they entered the building.
In neighboring Nepal, authorities have increased security and warned Tibetan exiles not to protest.
China says Tibet has always been part of its territory, but many Tibetans say their homeland was independent for centuries until Chinese troops invaded in 1950.
Beijing considers the Dalai Lama a separatist seeking Tibetan independence. But the Buddhist leader says he only wants greater autonomy for the Himalayan region.
China, an officially atheist state, asserted Sunday that it will choose who succeeds the Dalai Lama after he dies. Traditionally, Tibet's Buddhist priests search for the reincarnation of the Dalai Lama.
The 74-year-old Tibetan spiritual leader has suggested he may change that tradition by choosing his successor while he is still alive, and that a woman could hold the position.