BEIJING (REUTERS).- China's detention of internationally renowned artist Ai Weiwei has sparked a petition urging his release, exposing alarm among the nation's liberal intellectuals who see his case as a test of how far a crackdown to stifle dissent could reach.

Chinese officials have not commented on the whereabouts of Ai, who was stopped on Sunday from boarding a flight from Beijing to Hong Kong and taken away by border police. There is little doubt he has joined a lengthening list of dissidents and activists in detention or informal custody.

Ai has been out of contact; his mobile phone is off.

His wife, Lu Qing, told Reuters that police officers would not give her any information, and this detention appeared more serious than his recent run-ins with the government.

"This time it's extremely serious," she said, adding that she was considering retaining a lawyer.

"They searched his studio and took discs and hard drives and all kinds of stuff, but the police haven't told us where he is or what they're after. There's no information about him."

The disappearance of Ai, a burly, bearded 53-year-old avant-garde artist and designer who had a hand in designing the Bird's Nest stadium for the 2008 Beijing Olympics, has drawn condemnation from Western governments.

The United States, Britain and Germany denounced China's growing use of extra-judicial detentions against dissidents who the ruling Communist Party fears could spread calls for protests inspired by Middle Eastern uprisings.

On Tuesday, the United States embassy and European Union delegation in Beijing repeated those denunciations, illustrating how Ai's case could escalate into a diplomatic row.

Chinese activists are also increasingly alarmed about Ai's detention, and supporters in China and abroad promoted an online drive urging authorities to free him.

"Today, every one of us could become an Ai Weiwei," Ai Xiaoming, an academic and documentary-maker in southern China, who is not related to Ai Weiwei, wrote in an essay about the petition that circulated on overseas Chinese internet sites.

"What I meant was that Ai Weiwei is an artist, so he has more prominence than many others, but there are many other people facing the same situation," she said in a telephone interview on Tuesday.

"But I also meant that we can all also try to act like Ai Weiwei and speak out."

The online petition to "free Ai Weiwei" was launched on a Twitter microblog site (twitition.com/ao9m7), which China's wall of Internet censorship stops most Chinese people from seeing.

By Tuesday afternoon, it had more than 1,500 signatories, many of them apparently Chinese people with the skills and technology to jump past the censorship barriers.

Inquiries about Ai on China's most popular homegrown micoblogging site, Sina.com's "Weibo," are blocked. But many activists in China have followed the case by overcoming censorship or by word of mouth.

DOZENS IN DETENTION

Ai is the most internationally prominent target of a burst of detentions since February. While dozens of activists have been released, dozens remain locked away, and at least three have been formally arrested on broad subversion charges often used to jail dissidents.

Wang Ling, the wife of Teng Biao, one of Beijing's most prominent human rights lawyers, told Reuters that police officers told her Teng was "under investigation" but they declined to say what for or to let her visit him.

The crackdown goes beyond recent cycles of political tightening, said Chinese intellectuals. If Teng or other prominent lawyers are formally arrested, the outcry against the Party at home and abroad would be sure to grow.

"The most disturbing thing is that there is no sign of the government relaxing its grip this time around," Amnesty International's Asia-Pacific director, Sam Zarifi, said in a statement. "We fear that this is just a taste of things to come."

Up to now, Ai has been somewhat protected by his fame and by being the son of a famed Communist poet, Ai Qing. His extended detention suggested the Party was re-drawing the boundaries of what it would tolerate, said dissidents and scholars.

"The Party has unilaterally torn up the rules of the game. Before now there was a clearer sense of what could be said and when they would stop it or arrest people," said a journalist who declined to be identified, citing fear of losing his job.

He and others said leaders' worries about spillover from Middle East unrest was compounding the jitters that usually accompany the run-up to a leadership succession, with President Hu Jintao due to retire as Party chief late in 2012.

Ai Xiaoming, the documentary maker, likened the intent behind the crackdown on dissent to the armed suppression of pro-democracy protests in Beijing in June 1989.

"They may perhaps think about 1989 and how killing that many people made for 20 years of stability," she said. "Now they don't need to kill people, but by detaining people willing to speak out, they think they can snuff out criticism for a long time."


(Additional reporting by Sui-Lee Wee; Editing by Robert Birsel)

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