Prominent Chinese dissident Liu Xiaobo, a leading force behind a petition calling for democratic reforms, has been formally arrested for subversive activities, state media said Wednesday.

Activist groups said the move was a blow for human rights and political freedom in China while US House Speaker Nancy Pelosi urged worldwide condemnation.

china arrest democratic advocator liu xiaobo 250609 01 Liu, who has been detained since December, was arrested Tuesday for "alleged agitation activities aimed at subversion of the government and overthrowing the socialist system," Xinhua news agency said, citing Beijing police.

The 53-year-old writer, who was involved in the 1989 Tiananmen Square pro-democracy movement that was crushed by the army, has long campaigned through his writings for human rights and democracy in China.

He was taken into custody last year after signing Charter 08, a widely circulated manifesto calling for fundamental political and legal reforms to China's Communist Party-dominated system and respect for human rights.

The document was signed by about 300 Chinese scholars, lawyers and officials.

"Liu has been engaged in agitation activities, such as spreading of rumours and defaming of the government, aimed at subversion of the state and overthrowing the socialist system in recent years," Xinhua quoted a police statement as saying.

Liu had confessed to the charge, the statement added.

His lawyer, Mo Shaoping, said he was not informed of the arrest, but that police were still in the process of investigating the case. If formally charged Liu could get up to 15 years in prison, Mo said.

Beijing police declined to comment to AFP .

Wife under house arrest

The arrest comes amid tightened controls in China amid a series of sensitive political anniversaries this year.

China earlier this month passed the 20th anniversary of the crackdown on the 1989 Tiananmen Square protests with stifling security and next faces October's 60th anniversary of the founding of communist China.

china arrest democratic advocator liu xiaobo 250609 02 Mo said police had told Liu's wife, Liu Xia, that he might not be able to work as Liu's defence lawyer. Mo said this may be because he also had signed Charter 08.

Mo said he was preparing a formal request to be allowed to meet with Liu.

Liu Xia could not immediately be reached for comment.

Liu Xiaobo has been under a form of house arrest in an undisclosed location away from his home since December.

"The decision by the Chinese government to formally arrest Liu Xiaobo deserves the full condemnation from the international community," said Pelosi, who is second in line for the presidency after US Vice President Joe Biden.

"Liu's arrest for peacefully criticising his government and advocating for human rights violates provisions in China's constitution as well as international human rights standards," Pelosi said in a statement.

Nicholas Bequelin, a Hong Kong-based researcher with Human Rights Watch, said the arrest meant Liu would almost certainly go to prison, calling it "a pre-determined result."

"We believe that Liu Xiaobo has done nothing but exercise his right to freedom of expression and in no circumstances should he have been arrested," Bequelin told AFP .

Room for dissent is shrinking

Amnesty International also condemned Liu's arrest.

"This use of state security charges to punish activists for merely expressing their views must stop," it said in an emailed statement.

Bequelin said Chinese authorities had long tolerated Liu's dissident writings.

But he said his arrest made clear that hardline elements in the government blamed for a tightening of political controls since before last year's Beijing Olympics had gained the upper hand.

china arrest democratic advocator liu xiaobo 250609 03 "The Ministry of Public Security has seen its power considerably enhanced and they are more aggressive. The room for dissent is shrinking," he said.

Liu was jailed for nearly two years for his role in the 1989 Tiananmen protests and then again in the mid-1990s.

His case is the highest-profile dissident arrest since rights activist Hu Jia was arrested in December 2007 and sentenced four months later to three and a half years in prison for sedition.

It has drawn intense international criticism, with the European Union and the United States demanding his quick release.

Novelists such as Britain's Salman Rushdie and Italy's Umberto Eco, as well as Nobel literature laureates including Irish poet Seamus Heaney, have also campaigned for Liu's release.

-AFP