BEIJING – Outspoken Chinese artist Ai Weiwei was detained on Sunday as he tried to board a flight for Hong Kong and police later raided his studio outside Beijing, Twitter postings by his staff said.

The move comes just days after Ai, one of China's best-known artists, announced plans for a studio abroad to avoid official harassment and as Chinese authorities crack down hard on government critics.

Ai, who helped design Beijing's famed "Bird's Nest" Olympic stadium but who has antagonised the Communist Party government with his activism, was detained by customs officers at Beijing airport, the Twitter postings said.

Chinese authorities have rounded up scores of dissidents, activists, and right lawyers in recent weeks, with many placed under house arrest or disappearing into police custody.

The clampdown followed anonymous online calls which emerged in February for protests each Sunday around the country to demand political change in China and aimed at emulating those that have rocked the Arab world.

Ai had said Tuesday he planned to set up a studio in Germany to show his work, fed up with the hurdles of exhibiting in China, but would still use Beijing as his production and design base.

"It's very discouraging what's happening here and if I want to continue to develop my work, I have to find a base," said the burly, avant-garde artist.

The Twitter postings -- which indicated they were written by one of Ai's assistants -- said a group of police also arrived at his studio in Beijing's Caochangdi art district to execute a search warrant.

Police also took away eight of his staff members for questioning, a posting said, while his wife Lu Qing was under police custody at their home.

Ai's personal cell phone was turned off and calls to his studio and one of his assistants went unanswered.

A frequent critic of China's Communist Party leaders, Ai has repeatedly run into problems with the authorities in the past.

He said in February that his first large solo exhibition in mainland China was cancelled after organisers said the timing was too politically sensitive.

In January, his newly built Shanghai studio was demolished in apparent retaliation for his criticism of city policies, and he was blocked from leaving China in December ahead of the Nobel Peace Prize ceremony in Oslo for jailed Chinese dissident writer Liu Xiaobo.

Previously, Ai investigated school collapses in the massive 2008 quake in the southwestern province of Sichuan, which many believe were triggered by shoddy construction work.