China artist Ai Weiwei's Shanghai studio demolished

Artist Ai Weiwei has been highly vocal about human rights issues in his country

Chinese demolition workers have torn down the Shanghai studio of the artist Ai Weiwei - a move he says is linked to his political activism.

Mr Ai said the demolition crews arrived without warning on Tuesday and flattened the building within a day.

He originally had permission to build the studio, but later officials ordered it to be destroyed, saying he had failed to follow planning procedures.

Mr Ai has been increasingly vocal in his criticism of China's leaders.

The 53-year-old, one of China's most famous and controversial artists, said the demolition started in the night and he flew from Beijing to Shanghai as soon as he heard.

Mr Ai told the BBC Chinese service why he believed the building was destroyed: "They wanted to demolish it overnight without us finding out because they were worried the demolition would attract attention.

"We asked why it was demolished earlier than when we were told and they just answered that sooner or later, it would have been done anyway."

'Ridiculous'

In November, more than 400 supporters of the artist held a party at the $1.1m (£670,000) studio to mark its imminent destruction.

Mr Ai was unable to attend after being placed under house arrest.

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

Mr Ai Weiwei 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.

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.