Beijing , China ( CNN ) -- A Chinese artist and activist said Saturday that he has been placed under house arrest for planning a demolition party to `` observe '' a government order to raze his studio . Ai Weiwei said he had planned a concert and a river crab feast at the party in Shanghai on Sunday . About 800 people were expected to attend , he said . The term river crab is believed to make a political statement . The Mandarin word for river crab sounds like `` harmonious , '' a word some use to describe government censorship . Ai Weiwei opens London installation `` Sunflower Seeds '' Ai said he was put under house arrest until Sunday to prevent him from attending the party . `` Just recently I heard the new studio I built in Shanghai studio will be demolished all because of my activities , '' Ai said . `` So what is my activity ? My activity is very very simple , asking basic right for people to freely express themselves and also to find a new structure , a new way of communicating . Because I 'm an artist this is what I do and I believe in that . '' Ai said he was not allowed to leave his house , which was guarded by police . `` Please accept my deepest apologies , '' he tweeted to his guests in Shanghai . Ai said he chose to `` celebrate our life '' since the studio was going to be razed anyway . He has accused the Chinese government of trying to silence dissidents before . `` They crack down on everybody who has different opinions -- not even different opinions , just different attitudes , '' he told CNN earlier this year . `` Simply to have different opinions can cost [ dissidents ] their life ; they can be put in jail , can be silenced , and can disappear . '' The artist helped design the iconic Bird 's Nest stadium for the 2008 Beijing Olympics , but later called for a boycott of the games because he believed China was using them as propaganda . He has also held exhibits in Europe and the United States , and his work is on display at the Tate Modern gallery 's Turbine Hall in London , England .
Ai Weiwei says he had planned a party to `` observe '' a government order to raze his studio . Ai says he was not allowed to leave his house . His house is guarded by police , he says .