Artists and supporters of detained Chinese artist Ai Weiwei solemnly read out quotes from him on Wednesday ahead of the opening of two exhibitions of his work in London this week.

Lined up around 12 giant animal heads standing in the courtyard of Somerset House, they called for the Chinese government to free the man who has not been heard of since he was arrested at Beijing airport a month ago.

"Chinese government, release Ai Weiwei," shouted Patrick Brill, a British contemporary artist who works under the pseudonym Bob and Roberta Smith.

Gwyn Miles, the director of Somerset House Trust, told journalists the exhibition entitled "Circle of Animals/Zodiac Heads" was planned two years ago, "but doing it now shows support to Ai Weiwei".

"Like everyone who admires and respects the work of Ai Weiwei we are very upset by the news that he has been detained by the Chinese authorities," Miles said.

But she admitted that as a wave of international protests at his detention had failed to secure his release, "it is difficult to see what is going to have an impact".

The exhibition of 12 bronze heads on bronze poles, each weighing 360 kilogrammes (800 pounds), are enlarged re-creations of the traditional Chinese zodiac sculptures which once adorned the fountain clock of Yuanming Yuan, an 18th century imperial retreat outside Beijing.

In 1860, the site was ransacked by French and British troops, and the heads were pillaged. Just seven have been recovered -- the whereabouts of the other five remain a mystery.

In a statement accompanying the exhibition, Ai Weiwei says the work tapped into the issues of looting and repatriation, as well as returning to a long-running feature of his work -- perceptions of fake and copy.

The organiser of the readings, writer and broadcaster Ekow Eshun, said it was crucial to keep Ai Weiwei in the eye of the world's media.

"Everyone in the Western world is united to have his release. The most important thing is to show his work and to keep asking the question: 'Where is Ai Weiwei?'"

"All you can do is keep his art alive and in the public eye."

In another show opening in London on Thursday, the Lisson Gallery dedicates both its galleries to more works by the artist.

Ancient Chinese vases splashed in garish synthetic colours are meant to be a commentary on the way traditional values are corrupted by commercialism.

And a security camera sculpted from marble is the artist's view of the surveillance society of which he has fallen foul.

China said last week that other countries should stop commenting on Ai Weiwei's detention.

earlier related report
Suspect detained in Forbidden City theft: report
Beijing (AFP) May 11, 2011 - Police in Beijing Wednesday detained a 28-year-old man suspected of stealing several items from the Forbidden City, in a rare theft at China's ancient imperial palace museum, state media reported.

Police seized the suspect, Shi Baikui, Wednesday evening in southwest Beijing and he had confessed to the theft, Xinhua news agency said.

Some of the items had been recovered and the investigation was continuing, it said. Shi was from the eastern province of Shandong but no further details were released about him.

Officials at the Forbidden City earlier told police that seven items belonging to an exhibit on loan from a private Hong Kong museum and valued at up to 10 million yuan ($1.5 million) were stolen on Sunday, the Beijing News reported.

Police said a "suspicious" man had fled after being stopped by a palace museum worker, Xinhua said. Several items were later discovered to be missing from the temporary exhibition.

The stolen items, which date from the early 20th century, include jewellery boxes and women's make-up cases, reports said.

The items were taken from the Zhai Gong exhibit hall in the northeastern part of the sprawling palace, where the display was to continue until June 27, the Beijing News said. The section was closed to tourists following the incident.

The exhibit was on loan from the Liang Yi Museum, which is owned by a Hong Kong collector identified as Feng Yaohui, the paper said.

In the most recent theft attempt at the heavily guarded Forbidden City, police in 1987 captured a man identified as Xiang Dexiang, who was unsuccessful but was still sentenced to life in prison, the Global Times reported.

According to police records, only four thefts have been recorded at the Forbidden City between 1949 and 1987, the paper said.

Located in central Beijing, the Forbidden City was first built in the early decades of the 15th century and served as the imperial palace of China's Ming and Qing Dynasties.

It was transformed into the Palace Museum in 1925 after the fall of the Qing.