NEW YORK : An exhibit of sculptures by China's Ai Weiwei opened Wednesday in New York ahead of a world tour - but without the presence of the dissident artist, missing since his arrest a month ago in Beijing.

Mayor Michael Bloomberg opened the exhibit titled “Circle of Animals/Zodiac Heads” at the entrance to Central Park in Manhattan.

The mayor praised Ai as a beacon of creative courage and he called on China to release the missing artist.

“Ai Weiwei could not be here with us for the unveiling of his latest work,” Bloomberg said. “We do not know where he is, or when he will be released, that is very disturbing.” Bloomberg said he stood “in solidarity with the millions of people around the world who are hoping that Ai Weiwei is quickly and safely released.”

Ai, a harsh critic of China's Communist Party leaders, was taken into custody in Beijing on April 3 for unspecified “economic crimes”, sparking worldwide condemnation.

His huge bronze sculptures are based on the 12 animals of the Chinese Zodiac and are due to start a world tour after their New York opening.

Ai himself lived in New York for more than a decade, studying at the renowned Parsons School of Design. “He is among the millions who have come to our city, drawn by the lamp of liberty that shines from our shores,” Bloomberg said.

At the opening ceremony, artists, writers and public figures took turns to read out quotations from Ai's writings and interviews that touched on his belief in free speech and his artistic philosophy.

About the Zodiac sculpture, he was quoted as saying: “New York is the first cosmopolitan city I'm familiar with. It's not one kind of people, it's people (from) everywhere, and a lot of minorities. So I think it's a perfect place. It's a zodiac city.”