A bookseller who disappeared from Hong Kong and surfaced in mainland China has returned to the city, according to police.

Lee Bo, who is a British citizen, was last seen outside a publishing company’s warehouse in Hong Kong on 30 December.

He was widely believed to have been abducted and transported to the Chinese mainland.

He was the fifth Hong Kong-based bookseller to disappear, and the publishing house where they all worked specialised in salacious works about the Communist Party leadership.

That company, Mighty Current, was rumoured to have been planning to publish a book about Chinese President Xi Jinping’s love life.

Mr Lee’s wife had found the travel document he would have needed to cross the border legally at their home and reported him missing.

Poster of missing Lee Bo

Posters in Hong Kong had claimed Lee Bo was kidnapped by Chinese officials

He appeared on the pro-Communist channel Phoenix TV from an undisclosed location earlier this month, insisting he had smuggled himself across the border to assist with an investigation, and planned to renounce his British citizenship.

Despite strenuous efforts, British consular officials have been unable to gain access to Mr Lee in China to confirm this with him in person.

Hong Kong police say Mr Lee presented himself at the border on Thursday and repeated his assertion to immigration officials that he had travelled freely to the mainland to help with a court case against a friend.

They said he provided few details, and did not tell officers how he had crossed the border out of Hong Kong. They said he asked for his missing person case to be close, and left.

Pro-democracy lawmakers display portraits of Lee Bo, one of the five booksellers who disappeared from a local bookstore, during Chief Executive Leung's annual policy address in Hong Kong

Pro-democracy lawmakers in Hong Kong had staged protests

Oddly, when Sky News tried to contact Mr Lee’s wife, her phone rang as though it was in the Chinese mainland, before diverting to voicemail.

In a second interview with Phoenix TV, apparently recorded before he left for Hong Kong, Mr Lee said he was looking forward to seeing his son, but would soon return to the mainland to continue the investigation.

Human rights groups are far from convinced that the situation has been resolved.

“While we’re relieved to see Lee Bo return to Hong Kong, critical questions remain unanswered,” Sophie Richardson, China director for Human Rights Watch, told Sky News.

“Not least under whose authority he was taken to the mainland minus his travel documents, how he was interviewed by Phoenix TV while still being held, and whether he really intents to change his citizenship.

“Beijing still has a lot of explaining to do.”