Prominent Chinese artist Ai Weiwei said on Saturday he had been put under house arrest in connection with an argument with the government over the planned demolition of his studio in Shanghai.
"The police have announced that I am not allowed to leave my house," Ai told Reuters by telephone from his Beijing residence.
"It's to do with what's happening over my studio. They say that it has been illegally built and want to demolish it," he said, adding he did not know when that might happen.
"I expect my house arrest to end tomorrow evening," Ai said.
Some of Ai's supporters and friends plan to hold a "party" at the studio in Shanghai on Sunday to mark the demolition, but it was not certain if authorities would allow that to happen.
Beijing police could not immediately be reached for comment.
Ai is one of China's most famous contemporary artists. His career spans protests for artistic freedom in 1979, provocative works in the 1990s and a hand in designing the Bird's Nest stadium for the 2008 Beijing Olympics.
Ai's public comments, activities and art are some of the loudest, most flagrantly defiant forms of speech in China today, where government controls on the Internet and traditional media constrain civil society.
Ai has never been formally arrested, despite his occasional brushes with the law.
He gets away with being outspoken because of the prestige of his father, poet Ai Qing, because he picks his battles carefully and because his own art has brought wealth and fame overseas.
The Tate Modern in London is currently hosting a solo exhibition at its Turbine Hall of Ai's work, consisting of some 100 million individually made porcelain seed replicas, which visitors were originally invited to walk across.