Prominent Chinese Artist Ai Weiwei Detained and Missing

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The internationally acclaimed and controversial Chinese artist Ai Weiwei has been missing since Sunday morning after being detained while going through immigration at the airport in Beijing. Authorities separated him from staff he was travelling with and turned off his cell phone.

Shortly after Ai was detained, 40 police officers arrived at his studio and raided it, confiscating dozens of items and taking away eight of his assistants. A Twitter message sent from his office said, "There are police at the front and back doors, no way to go in or out." Ai's staff members were released a few hours later, but no one has heard from Ai Weiwei.

If he remains in custody, this will be the most high-profile detention yet in a government crackdown in which dozens of dissidents and activists have been swept up. All mention of Ai's arrest has been deleted from Chinese websites. And Beijing police officials have not commented.

Ai's assistant, who was travelling to Hong Kong with Ai when he was taken into custody, told the BBC, "I went back to check with the security officers and they said, 'He has other business. You go on the flight on your own.'"

Reporters Without Borders was quick to denounce Ai's detainment. "The Chinese government is stepping up its harassment of the remaining prominent dissidents and is trying to silence all of its critics. We urge the international community to react firmly to the arrests...that are taking place at an unprecedented rate."

The arrests appear to be related to the government's concern over an online call for a "jasmine revolution." Some of those detained have been charged with "inciting subversion of state power," the same charged Nobel Peace Prize winner Liu Xiaobo faced. He is serving an 11 year prison sentence. Ai Weiwei was blocked from leaving China in December ahead of the Nobel Peace Prize ceremony in Oslo.

Dean Peng, an outspoken academic and dissident, spoke to ABC News recently about the crackdown.

"So far, Chinese authorities reacted to jasmine event hysterically, and indeed, stupidly. It seems that the only way that the authorities are able to think of to deal with crisis is to arrest and kidnap people."

Chinese Dissident Ai Weiwei Vanishes Into Official Custody

On Feb. 24, amid the jasmine campaign, Ai posted on Twitter: "I didn't care about jasmine at first, but people who are scared by jasmine sent out information about how harmful jasmine is often, which makes me realize that jasmine is what scares them the most. What a jasmine!"

The outspoken Ai was the artistic director for the "Bird's Nest" Olympic Stadium, but later turned critical of the Games.

As a frequent critic of China's Communist Party leaders, Ai has repeatedly run into problems with authorities.

In 2009, in Chengdu, Ai was beaten so badly that he required surgery to have blood drained from his brain. He was there to collect the names of children who died in the Sichuan earthquake after protesting that the schools were shoddily built. Ai composed a body of work, combining video footage of him talking with police with photographs of him in the hospital with a drain coming from his scalp.

Ai, who currently has a show on at London's Tate Modern gallery, was prevented from having a solo exhibition of his work at a Beijing gallery because it was too politically sensitive. And in January, authorities demolished his Shanghai studio.

Ai Weiwei recently announced plans to open a studio in Berlin so he could work freely. He told the German press agency that he hoped to spend "as little time as possible" there. He added, "However, there will be no choice if my work and life are somehow threatened."