Britain, the United States and the European Union, as well as leading figures in the art world, have joined the growing international outcry over the detention of the outspoken Chinese artist Ai Weiwei and Beijing's wider crackdown on dissidents and activists.

Officials detained Ai on Sunday morning as he attempted to board a plane for Hong Kong. No one has been able to contact him or his friend Wen Tao, who was detained on the same day.

Ai is China's best known artist and designed the Olympic Bird's Nest stadium, but he has been an outspoken critic of the government. Last year he was placed under house arrest after announcing a party to mark the forced demolition of his studio in Shanghai.

Ai's wife, Lu Qing, told Reuters: "This time it's extremely serious. 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."

The Chinese Human Rights Defenders (CHRD) network said that another four artists from Beijing were detained on 24 March after a performance art event where some pieces touched on the crackdown and the "jasmine revolution".

Asked about concerns for the whereabouts and physical safety of those reported missing, a foreign ministry spokeswoman, Jiang Yu, said last week: "China, as a country under the rule of law, protects its citizens' basic rights and freedoms – including freedom of expression – but citizens while exercising their rights have an obligation to abide by the law and should not bring harm to the public interest."

http://www.guardian.co.uk/artanddesign/2011/apr/05/ai-weiwei-detention-china