BEIJING — Chinese authorities have detained a highly regarded Tibetan monk and 16 of his supporters, a Tibetan writer said Friday, as Beijing tightens its grip over the region.

The writer, Tsering Woeser, said that rights lawyer Tang Tianhao confirmed the detention of Karma Tsewang, a popular monk in Nangqian county in western Qinghai province. Aside from preaching Tibetan Buddhism, the monk is known for his work on disaster relief, environmental protection and teaching youth the Tibetan language.

Tsering Woeser said Karma Tsewang was taken away by police Dec. 6 while traveling on business in the city of Chengdu. She said the monk was taken to Chamdo prefecture, where he has been detained since.

More than 100 laypeople and monks in Nangqian petitioned the government Dec. 18 to release Karma Tsewang, but 16 of them were detained in the following days, the writer said.

Tsering Woeser said she obtained the information from local residents as well as Tang, who declined to speak to the media out of fear of governmental retaliation but asked Tsering Woeser to relay the information.

The writer said the authorities have warned the families of Karma Tsewang and of the detained supporters not to hire lawyers.

Police in both Chamdo and Nangqian said they had no knowledge of the case. Calls to local governments were either unanswered or answered by people who said they did not know about the case.

Tsering Woeser said that Tang, who was retained by Karma Tsewang’s family, had been denied visits with the monk in Chamdo.

Tsering Woeser said she is concerned that any conviction against the popular monk could upset local residents and cause unrest.

For decades, ethnic Tibetans have resented Beijing’s strict limits on Buddhism and Tibetan culture, as their spiritual leader, the Dalai Lama, remains in exile.

Although Beijing says it has made vast investments to boost the region’s economy and improve the quality of life for Tibetans, many Tibetans say Beijing’s economic policies there have mainly benefited ethnic Chinese migrants.

More than 100 people have self-immolated since 2009 to protest China’s rule over Tibetan areas.