The daughter of Hong Kong-based bookseller Gui Minhai confirmed on Monday that her father has been detained by Chinese authorities for a second time.

Angela Gui told international broadcaster Radio Sweden that the publisher of political gossip books about China's political elite, was seized on Saturday while traveling with two Swedish diplomats on a train to Beijing.

Ten plainclothes police officers boarded the train just outside the Chinese capital, "grabbed him and just took him away," she told the station.

Daughter's anguish

"It's quite clear that he has been abducted again and that he's held somewhere in a secret location," she said, adding that she was worried because of his health condition.

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Gui had been traveling to Beijing to see a Swedish doctor after being diagnosed with a neurological disease that developed while in custody the first time, his daughter said. The health visit had been arranged in conjunction with the Swedish embassy.

But the South China Morning Post cited friends of Gui as saying he may have been traveling to Beijing to pick up a new Swedish passport.

Passing on secrets?

The New York Times reported that Chinese officials told Swedish diplomats that Gui was this time suspected of sharing secrets with Swedish authorities.

The book publisher, who took Swedish nationality in 1992 and who works from Hong Kong, first disappeared while at his Thai holiday home in late 2015.

He later turned up in custody in China along with four other men from the same Hong Kong publisher, which is well known among mainland Chinese tourists for its tabloid-style books.

Their case sparked international concern amid allegations of extrajudicial abduction across borders.

While his colleagues were released a few months later, Gui was held until October last year.

One of the detained men claimed upon his release that their confessions had been scripted and stage-managed.

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The men's disappearance sparked concerns about the erosion of the rule of law in Hong Kong, a former British colony that returned to Chinese rule in 1997, with a high degree of autonomy guaranteed by Beijing until 2047.

The territory is generally considered a safe haven for dissenting voices, has a free press and is a hub for publishers of books banned in China.

But in recent years Beijing has attempted to assert its authority, which opponents fear threatens the principle of one China, two systems (of government).

Sweden summons ambassador

Sweden's foreign ministry said on Monday Foreign Minister Margot Wallstrom had summoned China's ambassador over the reports of Gui's detention.

"The Swedish government is fully aware of what happened on January 20. Firm actions have been taken at a high political level and we have been in contact with Chinese officials who have promised us immediate information about his condition," the official, Patric Nilsson, said.

mm/se (AP, dpa, Reuters)