Chinese police have detained several people after pro-Tibet protests in south-west China, campaign groups say.
The protests flared at the weekend in Litang county, in Sichuan province.
A number of Tibetans were beaten and 21 detained, the Free Tibet group and the Tibetan Centre for Human Rights and Democracy (TCHRD) said.
The incident comes ahead of the 50th anniversary of the exile of the Dalai Lama, the Tibetan spiritual leader, and follows violent protests last year.
China does not allow foreign journalists unrestricted access to Tibet or restive areas surrounding it, making it extremely difficult to verify reports from the region.
A police office in Litang told Reuters news agency that he "did not have any such information".
According to London-based Free Tibet, the protest began when a Tibetan monk shouted pro-Tibetan slogans in a market place on Sunday. Police beat those who joined him and arrested him, the group said.
China says Tibet was always part of its territory
Tibet enjoyed long periods of autonomy before 20th century
1950: China launched a military assault
Opposition to Chinese rule led to a bloody uprising in 1959
Tibet's spiritual leader the Dalai Lama fled to India
Another protest on Monday drew more people, prompting further detentions and violence, it said.
India-based TCHRD said that a total of 21 people had been detained. Two of the detainees sustained serious injuries, the organisation said.
The protests come nearly a year after a series of demonstrations in and around Tibet - the worst violence in the region for two decades.
China says rioters killed at least 19 people, but Tibetan exiles say security forces killed dozens of protesters.
Those protests began after Tibetan monks marked the 49th anniversary of a failed uprising against Chinese rule that forced the Dalai Lama into exile.
The highly sensitive 50th anniversary comes next month.
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