Chinese Avant-Garde artist Ai Weiwei is pictured at the Theater am Goetheplatz in Bremen, northern Germany. (FOCKE STRANGMANN/AP)

Fears for the safety of one of China’s best-known artists are growing amid international condemnation of his extra-legal disappearance at the hands of the country’s increasingly repressive state security apparatus.

Relatives of Ai Weiwei, whose “Sunflower Seeds” exhibition is on display in London’s Tate Modern gallery, said Tuesday evening that they still had no idea of his whereabouts. He was detained at a Beijing airport on Sunday and led away by airport security personnel.

Until now, Ai had been seen as immune from the kind of persecution increasingly meted out to other activists, thanks to his stature as a rich and internationally famous artist.

He has also enjoyed the special protection afforded to well-connected children of revolutionary heroes. His father was a renowned communist poet who in 1949 stood alongside Mao Zedong in Beijing’s Tiananmen Square when the chairman declared the birth of the People’s Republic.

But now, even Ai’s friends, relatives and associates have been warned not to speak to journalists, and his wife and eight employees were temporarily detained Sunday after police raided his Beijing home and studio. A member of Ai’s family said that at least one of his associates remains in custody.

Human rights groups say Ai is in grave danger of being tortured and is probably being deprived of medicines he needs regularly.

Britain, France, Germany, the United States and the European Union have condemned Ai’s disappearance and expressed concern at a wave of similar cases in recent weeks, in which prominent human rights activists and Internet bloggers have been detained or have vanished.

The ongoing campaign of repression in China is thought to be related to anonymous online calls for a peaceful “jasmine revolution,” emulating calls for democracy sweeping through the Middle East and North Africa.

— Financial Times