Rights campaigners dismissed an apparent confession by a missing Hong Kong bookseller paraded on Chinese state television as "worthless" and a "smokescreen" Monday as the city's leader distanced himself from the case.

Gui Minhai, a Swedish national, is one of five missing booksellers from a Hong Kong-based publisher known for salacious titles critical of the Chinese government.

Their disappearance has sparked alarm in the southern Chinese city which is guaranteed a range of freedoms not seen on the mainland.

In his confession on state broadcaster CCTV Sunday Gui said he had returned to China to "take legal responsibilities" for killing a college student in a car accident 11 years ago.

Weeping Gui said he had fled the mainland after he was convicted of the crime, despite only receiving a two-year suspended sentence.

Amnesty International's East Asia director Nicholas Bequelin said Gui's confession raised more questions than answers.

"From the legal standpoint the video is worthless," he told AFP.

"Where is he? Under what authority is he detained? What are the circumstances under which he gave this interview? We cannot exclude the possibility that he made the statement under duress," he said.

The disappearances have fuelled growing unease in Hong Kong over the erosion of freedoms in the semi-autonomous city, which was handed back to China from Britain in 1997.

But despite deep public concern, Hong Kong leader Leung Chun-ying refused to discuss Gui's case.

"The Gui Minhai case has not been reported to the Hong Kong police or the Hong Kong government," he told reporters at a financial forum in Hong Kong.

Swedish deputy minister for finance Per Bolund -- also speaking at the financial forum -- said Stockholm "is quite concerned about the development" and asked for more "openness" from the mainland authorities, according to the South China Morning Post.

The Swedish consulate in Hong Kong said it had no comment.

Gui is thought to have gone missing from Thailand, where he has a holiday home.

- 'Smokescreen' -

Leung said he attached "great importance" to any new information on another bookseller, Lee Bo, the only one of the five men to have disappeared in Hong Kong.

The other three men went missing from southern mainland cities.

Lee's disappearance raised fears that Chinese security authorities were working in Hong Kong's territory, against the city's laws.

A letter, purportedly from Lee, was published Sunday taking aim at Gui on Hong Kong news website Headline Daily.

"He killed a person in a drink-driving crash and irresponsibly fled overseas," it read.

"This time he has implicated me," it said, without giving any further detail.

All five men worked for the Mighty Current publishing house which operates a bookstore in the commercial heart of Hong Kong.

Lee Cheuk-yan, a pro-democracy lawmaker in Hong Kong, said of the Gui confession that China was "trying to hide the fact that they are detaining him for the bookstore".

"The traffic accident has nothing to do with it and there was nothing in the video that says how he ended up in China," he said, describing the broadcast as a "smokescreen".

CCTV's website ran a news report in 2005, in which a man named Gui Minhai was said to have fled overseas in 2004 after he was given a two-year suspended sentence for killing a 23-year-old college student in the eastern city of Ningbo.

While the report could relate to the missing bookseller, there are nevertheless discrepancies.

CCTV says Gui was 46 in 2005, but on Sunday state news agency Xinhua gave his current age as 51.