Four "Tibet independence" advocates were detained here on Tuesday morning after clashing with police during a rally outside the Chinese embassy.
A dozen of demonstrators tried to break through a police line guarding the embassy，witnesses said.
Some demonstrators grappled with the police during the rally.
This year marks the 50th anniversary of the democratic reform in China's Tibet Autonomous Region.
Fifty years ago, the Chinese central government foiled an armed rebellion which was started on March 10 by the Dalai Lama and his followers to block the reform of the feudal serfdom in Tibet and split the region from China.
On March 28, 1959, a new local Tibetan government was formed, freeing millions of Tibetan serfs and slaves, who accounted for more than 90 percent of the then population in the region.
The Dalai Lama and his followers, since their exile, have continued to pursue either disguised or open activities in an attempt to separate Tibet from China and restore feudal serfdom in the region.
On March 14 last year, followers of the Dalai Lama staged riots in Lhasa to put pressure on the central government. Their violence resulted in 18 deaths of civilians and a huge loss of properties.
(Xinhua News Agency March 10, 2009)