A Beijing-based columnist has gone missing while on his way to Hong Kong, his lawyer has told the BBC.
No-one has had contact with Jia Jia since Tuesday night when he was set to board his flight. His wife has reported him missing.
He is said to have warned an editor friend about publishing an anonymous letter calling for President Xi Jinping's resignation.
The letter appeared on a state-linked site but was swiftly taken down.
It is unclear who authored the letter, which had the byline "loyal Communist Party supporters". Mr Jia had reportedly insisted he had no connection to the letter.
The incident appears to be the latest in a string of high-profile censorship incidents, amid a ramp-up of state campaigns aimed at burnishing Mr Xi's image.
What we know
Mr Jia, who is in his 30s, is known for writing socio-political commentaries for the online news portal Tencent. He was due to fly from Beijing to Hong Kong on Tuesday when he became uncontactable.
The newspaper Apple Daily quoted Mr Jia's wife as saying she last spoke to him at 20:00 local time on Tuesday, and he told her he was about to board the plane to Hong Kong.
She added that Mr Jia was due to arrive at a friend's home that night, but he never arrived. He also missed a lunch appointment the next day.
His lawyer, Yan Xin, told the BBC: "We don't have any clue who took him away and why... there is [a] great possibility that he was taken away from the airport."
"His wife has not received any official document on Jia Jia's whereabouts and status."
Mr Yan added that attempts to find Mr Jia's flight booking record had failed, and he and Mr Jia's wife were checking with immigration authorities.
What the letter said
The letter in question raised eyebrows when it appeared on the state-linked news site Watching, also known as Wujie News, on 4 March.
Addressed to Mr Xi, it called for him to step down, accusing him of gaining "excessive power" and creating a "personality cult", and ran through a list of criticism of his rule ranging from his diplomatic policies to his economic decisions.
