BEIJING » A phalanx of Beijing police officers confined the prominent artist and activist Ai Weiwei to his north Beijing home on Friday, a move he suggested came at the behest of unnamed but powerful political figures in Shanghai who feared that he was about to embarrass them.

If so, they were correct.

Ai had planned to fly to Shanghai on Friday to prepare a Sunday goodbye party at his million-dollar art studio meant to draw attention to its pending destruction. In telephone interviews this week, Ai said he built the studio only after Shanghai officials, on a campaign to burnish the city’s cultural credentials, implored him to. But last year, they ordered the finished building demolished at the command of anonymous higher-ups.

Ai’s response was the party, to be attended by eight rock bands and up to a thousand supporters from around China. But on Thursday night, he said, the officers came to his home and asked him not to go to Shanghai.

On Friday, after he said he was going anyway, the officers placed him under house arrest — reluctantly, Ai said.

"They’re sorry, very sorry," he said by telephone from his home. "They say they understand me and really agree, but this is really beyond what they can do."

Ai said the officers told him that "Shanghai is very nervous" about the party. Like Ai, however, they did not know precisely who in Shanghai was nervous, or how they managed to arrange his confinement in a city 650 miles away.

Ai said he did not even know why the unnamed Shanghai officials had ordered his studio demolished, although he had his theories.

This is not the first run-in with the authorities for Ai, an artistic polymath who seems to be alternately tolerated and hectored by higher-ups. An internationally known sculptor, filmmaker, architect and performance artist, he helped design the Bird’s Nest stadium for the 2008 Beijing Olympics, then renounced his role after deciding that Chinese leaders had politicized the Games.

He was allowed to fly to Munich last year to stage a major exhibit that excoriated the government’s handling of children’s deaths in the 2008 Sichuan earthquake. Yet months before, he was so severely beaten by the police in Chengdu, the capital of Sichuan province, where he had gone to testify in the trial of a fellow activist, that he needed surgery to drain blood from his brain.

Ai’s latest run-in with Shanghai officials appears to exemplify that love-hate relationship.

As he tells it, he was approached more than two years ago in Beijing by the mayor of one of Shanghai’s districts — a government unit not unlike an American city ward — and beseeched to build a studio on an abandoned plot of farmland. Initially suspicious — "I told my assistant we’re not going to deal with government anymore," he said; "there’s no honesty there" — he relented when the mayor flew to Beijing for a personal appeal.

Ai said he worked closely with the district to rehabilitate an abandoned warehouse on the site, spending about $1 million to create a vast working space fronting on a lake with a sawtoothed roof and sides laced with a concrete grid. Other artists began building their own adjacent studios.

Then last July, as work was wrapping up, there came a city order to tear down the warehouse.

"They said only we received the notice," he said. "The other artists did not. We said, ‘Why?’ and they said, ‘Well, you should know, because of Ai Weiwei’s activities."’

Which activities offended someone is, of course, not known. But Ai said he suspected he rankled officials in 2008, when his blogging on the case of Yang Jia, who murdered six Shanghai policemen after being arrested and beaten for riding an unlicensed bicycle, created a national sensation. Yang was later executed. He said officials also might resent his documentary this year on Feng Zhenghu, a lawyer and activist who spent more than three months in Tokyo’s Narita Airport after Shanghai officials denied him entry to the country.

Whatever the reason, Ai said, the district official who first recruited Ai returned to Beijing this week, apologizing profusely and promising to compensate him for the cost of the renovation if he would leave.

"I said, ‘Why? It took so much effort and energy, and you didn’t give us a clear reason,"’ he said. "But they cannot really answer these questions. So I realize it’s inevitable. They’ll destroy the building."

At the planned goodbye party for the studio, in lieu of chips and dip, Ai planned to serve river crabs — a sly reference to the Mandarin word hexie, which means both river crab and harmonious. Among critics of China’s censorship regime, hexie has become a buzzword for opposition to the government’s call to create a harmonious society, free from dissent.

In short order, 800 supporters from across China made plans to attend, and eight bands volunteered to play at the event. "They already call it Woodstock," he said Wednesday in an interview. "I think it’s nice. It shows a kind of understanding and solidarity."

On Friday, Ai said he thought the unnamed Shanghai powers were taken aback by the attention to the demolition and the party and reacted in typical fashion. And by doing so, they created a piece of performance art that called more attention to the embarrassment they were seeking to suppress.

"They put you under house arrest, or they make you disappear," he said. "That’s all they can do. There’s no facing the issue and discussing it; it’s all a very simple treatment.

"Every dirty job has to be done by the police. Then you become a police state, because they have to deal with every problem.

"I think they hate me," he said. "But I never imagined they would destroy an entire building."

© 2010 The New York Times Company