A media rights group is urging China to free a Tibetan Internet writer who it says has been in detention for weeks without charge.
International PEN issued the appeal for the release of Kunchok Tsephel Gopey Tsang on Tuesday in an open letter to Chinese President Hu Jintao.
The London-based group said Chinese authorities arrested the 39-year-old Tibetan man on February 26th at his home in a heavily Tibetan area of southern Gansu province.
China has tightened security in the area in recent weeks to prevent a repeat of last year's Tibetan protests, in which Tibetans in southern Gansu rallied in large numbers and damaged government buildings.
PEN said authorities have previously arrested the Internet writer and shut down his Web site (www.tibetcm.com) several times.
In separate news, a U.S.-based advocacy group says Chinese authorities have given long prison sentences to two men for engaging in nonviolent protests in another minority region in China's northwest
The American Uighur Association says China sentenced one man to 15 years in prison and the other to eight years.
China's official Xinhua news agency said police in the Xinjiang Uighur Autonomous Region arrested a man for spreading on the Internet allegedly false rumors of ethnic conflict.
Earlier Tuesday, Chinese police confirmed that a bomb blast has damaged a government office in a majority Tibetan region of southwest China. Police said the explosion happened Monday in Batang county in Sichuan province's Ganzi Tibetan Autonomous Prefecture. No casualties were reported.
Chinese state media blamed the attack on "terrorists." China has tightened security in Tibet and neighboring Tibetan regions to try to prevent Tibetans from marking this month's anniversary of a failed 1959 uprising against Chinese rule.
Tibetan rights groups have reported several small anti-China protests in Tibet and nearby areas in recent days.