Reveal missing blogger: Amnesty

Rights group Amnesty International has called on the Chinese government to reveal the whereabouts of an Australian political blogger believed detained in the communist country.

Australia's foreign ministry is urgently trying to trace Yang Hengjun, a former Chinese diplomat who is now based in Sydney and is an Australian citizen.

Yang was last heard from on Sunday when he rang a colleague to say he was at Guangzhou airport in southern China and was being followed by three men.

Amnesty said those close to him believe he is being held by Chinese authorities.

"Yang Hengjun's disappearance is extremely worrying, especially as it comes during one of the biggest round-ups of activists and critics for years," said the group's deputy director for the Asia Pacific, Catherine Baber.

"He joins a long list of peaceful reformists who have gone missing or been arrested in China in the last month."

At a foreign ministry briefing in Beijing on Tuesday, a Chinese government spokeswoman said she had not heard of Yang and had no information about him.

Australia's foreign ministry said the government was urgently seeking to confirm his whereabouts and well-being.

Australia's Consul-General in Guangzhou has raised the matter with provincial and municipal-level Chinese authorities, while the Department of Foreign Affairs had spoken with the Chinese embassy in Canberra, it said.

Rights groups say Chinese authorities have been on edge since calls for protests emulating those sweeping the Arab world began in February and have since warned, placed under house arrest or detained up to 100 activists.

On Tuesday, China formally charged two activists on charges of "inciting subversion" amid the widening crackdown, which some say is the harshest in 15 years.

"There is no sign of this crackdown easing," Baber said, adding that Amnesty feared Chinese authorities were moving to treat any peaceful expression of support for reform as subversion.