Party held without detained Chinese artist Ai Weiwei

Image caption, Weiwei's supporters gathered on Sunday at his studio in the suburbs of Shanghai

Supporters of Chinese artist Ai Weiwei have thrown a party at his studio in Shanghai - an event he could not attend after being placed under house arrest.

Weiwei - creator of the sunflower seed installation at London's Tate Modern - had intended to be at the party, held to mark its imminent forced demolition.

On Friday, however, he said he was being prevented from leaving his home in Beijing by the Chinese authorities.

More than 400 people gathered on Sunday at the $1.1m (£670,000) studio.

Local authorities in Malu township have declared the building illegal, claiming proper application procedures were not followed.

Ai Weiwei has called the demolition order "ridiculous", claiming he had been told the edifice might be spared if he agreed to donate it for use as an agricultural museum.

"The government can make up any kind of rules they want," he is quoted as saying by the Reuters news agency.

Image caption, The artist has been highly vocal about human rights issues in China

He said he had been told not to leave his house and that officials were parked outside in a van to make sure he did not try.

Sunday's event took place without incident, with Weiwei's supporters making a light-hearted statement by eating river crab.

The Chinese name for river crab - "he xie" - sounds like the word for "harmonise", a euphemism often used by the Chinese authorities for censorship.

Born in 1957 in Beijing, Ai Weiwei has played a key role in contemporary Chinese art over the last two decades.

The artist, who helped create the Olympic "Bird's Nest" stadium in his home city, has been highly vocal about human rights issues in his country.

His latest work - a giant installation made up of hundreds of thousands of tiny, hand-painted replica sunflower seeds - is currently on display in the Turbine Hall of London's Tate Modern gallery.

Visitors were initially invited to walk on the seed bed but are now prevented from doing so after concerns over porcelain dust.

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