Beijing ? China is launching a security sweep in Tibet ahead of one of the region’s most sensitive anniversaries in years, with state media saying at least 81 people have been detained.

Tibet independence advocates said Wednesday the anti-crime crackdown in the Himalayan region appeared aimed at intimidating Tibetans ahead of the 50th anniversary of the failed uprising that saw the Dalai Lama flee into exile.

China has been preparing for the possibility of more unrest in Tibet since deadly rioting in the capital Lhasa on March 14 last year sparked the biggest anti-government protests among Tibetans in decades — and a major military crackdown.

China claims Tibet has always been part of its territory, while many Tibetans assert their Himalayan region was virtually independent for centuries.