An award-winning Chinese photographer has been missing and his wife is apprehensive that he might have been arrested by state security officers while visiting China's far-flung western Xinjiang region.
Lu Guang, a three-time World Press Photo award winner, had been invited to take part in photography events in the regional capital, Urumqi, in late October, his wife, Xu Xiaoli, said in online posts.
She lost touch with her husband on November 3 while he was travelling alone in the southern city of Kashgar, and has not heard from him since, Xu said.
She later contacted the wife of the person who had invited Lu to Xinjiang and was told both men had been taken away by state security officers, Xu said.
The Xinjiang regional government did not immediately respond to a request for comment by Reuters.
Xu, however, said that her husband's detention was confirmed to her by authorities in Lu's hometown Yongkang in Zhejiang province.
"I'm extremely worried, and hoping for his safe return home as soon as possible!" Xu posted on Twitter.
Yongkang police told AFP news agency that they were unaware of the situation.
Someone who picked up the phone at the police department in Kashgar hung up after hearing the call was from AFP.
At a regular news briefing in Beijing, Chinese foreign ministry spokesman Geng Shuang said he was not aware of the case.
"He went to Kashgar alone," Xu, who lives in New York City, told Reuters on Tuesday.
"Later, it was both him and the friend who were taken away."
Talking to Al Jazeera, Sophie Richardson of Human Rights Watch (HRW) said she has called on Chinese authorities "to immediately confirm and clarify... the whereabouts and well-being" of the photographer, who is a US green card holder.
"That's an obligation for them," she said.
Richardson added that it is "not terribly credible" for Chinese authorities to not have any information about the status of Lu.
In a statement to Al Jazeera, Patrick Poon of Amnesty International noted that Lu "is famous for his photographs of ordinary citizens in China".
"He went missing in Xinjiang most probably because the Chinese authorities would be afraid that he would take pictures in Xinjiang and expose the real situation there," Poon said.
"We call on the Chinese government to immediately disclose Lu Guang's whereabouts and release him as there is no evidence to show that he has violated any criminal offences."
Outcry over treatment of Uighur Muslims
Beijing has faced an outcry from activists, academics, foreign governments and the United Nations rights experts over mass detentions and strict surveillance of the Uighur Muslims and other Muslim groups in Xinjiang.
Chinese authorities routinely deny any ethnic or religious repression in Xinjiang and say its measures are needed to combat the influence of religious extremism.
Xu said she had not received any official notice of Lu's arrest and had been unable to contact Xinjiang police.
"December 4 is our 20th wedding anniversary. He was meant to celebrate with us together," Xu said in an online post.
"Ever since I lost touch with him, the days have dragged on like years."
Lu's 25-year career as a photographer has produced many award-winning photos which delve into the dark side of China's economic development and societal changes, documenting industrial pollution, worker abuse, AIDS-plagued villages, and the illegal export of African timber to China.
Lu had planned to travel from Xinjiang to southwestern Sichuan province on November 5 and rendezvous with a friend, who was unable to reach him, his wife said in a statement posted on Twitter.
Foreign journalists travelling to the region are frequently detained and followed by police to prevent and obstruct reporting on the internment camps and treatment of Uighurs.
HRW's Richardson said that like the case of international artist Ai Weiwei and actress Fan Bingbing, Chinese authorities have demonstrated that it has "no trouble effectively taking people off the grid".
"Each of these cases makes painfully clear how lawless China is," Richardson said, as she urged governments to come together "to create pressure on the Chinese government" to address the human rights situation in Xinjiang.
With additional reporting by Ted Regencia in Doha.