A global campaign was gathering pace last night for the release of Chinese dissident artist Ai Weiwei, who was detained by authorities on Sunday while attempting to board a flight from Beijing to Hong Kong.
Tate director, Sir Nicholas Serota, and the sculptors, Antony Gormley and Anish Kapoor, joined representatives from London's Somerset House – where Mr Ai was due to unveil a public installation next month – and Danish-Icelandic artist Olafur Eliasson, a close friend of Mr Ai's, in calling for the artist's immediate release. France and Germany also demanded the release of the artist, who revealed last week that he was planning to build a studio in Berlin.
"I appeal to the Chinese government to urgently provide clarification and I expect Ai Weiwei to be released immediately," the German foreign minister, Guido Westerwelle, said in a statement.
Mr Ai, 53, was taken from Beijing airport by security personnel. Police later raided his studio.
At the time of going to press the artist was "still missing", according to his lawyer, Pu Zhiqiang.
The artist's Sunflower Seeds Unilever Series installation is on display in Tate Modern's Turbine Hall until 2 May.
"The artist remains un-contactable and his whereabouts are unknown," said Sir Nicholas Serota. "We are dismayed by developments that again threaten Weiwei's right to speak freely as an artist and hope that he will be released immediately."
Mr Ai has documented the arrest of prominent fellow artists and activists on his Twitter account, where he has 73,000 followers.
"I would call on all cultural institutions globally to voice their protest against all kinds of behaviour which we haven't seen since the days of Stalin," said Gormley.
"I think he is one of the bravest voices to come out of China and as an artist I think he has fought tirelessly to make artistic freedoms available to others. In 21st-century China he is a lone voice." Kapoor said: "Mr Ai Weiwei is first and foremost an artist and he uses this position to speak out for freedom inside and outside of China.
"We all need to fight for freedom and I deplore the Chinese government's short-sighted need to withhold such freedom of expression." Eliasson said: "I am upset and I condemn the fact that the Chinese government is restraining his freedom in this way.
"I am saddened that they have to use policies from the Middle Ages to suppress freedom of speech."
The artist's first public installation in London, entitled "Circle of Animals", is scheduled to open on 12 May at the capital's Somerset House.