A Uygur Aids activist from Xinjiang was detained for allegedly endangering state security on the same day as outspoken Uygur academic Ilham Tohti was taken away by police, a former colleague said.
Akebaier Yiming was detained in Urumqi on January 15 when he returned to Xinjiang to attend his father's funeral, the Aids advocacy group Aizhixing Institute said.
Yiming's family received a notice from police saying he had been formally arrested on suspicion of "endangering state security", the institute's founder Wan Yanhai said. Yiming's friends and colleagues confirmed his arrest but did not know if his arrest was connected to Tohti's case, Wan said.
Tohti, a Beijing-based Uygur academic who has criticised government policy in Xinjiang, was taken into custody in January after police searched his home in Beijing. He was later charged with spreading separatist ideas.
Exiled Uygur groups have criticised Tohti's arrest, and accused the authorities of suppressing voices critical of their policies after a series of violent attacks that were have blamed on Muslim separatists from Xinjiang.
Yiming, 32, works at a medical research centre in Beijing and he was not noticed missing by friends and colleagues until the end of the Lunar New Year holiday last month, Wan said.
"We didn't dare to look for him in a very high-profile way because looking for a Uygur man is pretty sensitive," he said. "We were unsure then if anything had happened to him, and we feared we would bring him trouble."
The Aizhixing Institute supports Aids prevention on the mainland and Yiming was closely involved in the group's campaigns to raise awareness in the Uygur community, Wan said.
He had worked at the non-governmental medical research centre in Beijing since he left the institute in 2008, tackling drug use and HIV prevention.
Wan said Aizhixing staff were sometimes followed by police during their duties.
Yiming was known to be in contact with a website founded by Tohti for news and commentaries on Uygur issues, Wan said.
Additional reporting by Verna Yu