Chinese dissident artist Ai Weiwei has returned to Twitter following a long silence after his release from detention in June when he was barred from giving media interviews as part of his bail conditions.

Ai tweeted on Saturday for the first time since he was taken into custody at Beijing's international airport on April 3 while trying to board a flight to Hong Kong.

He posted several tweets on Sunday, including: "Ten dumplings for lunch, regained three kilos."

Twitter is officially blocked in China but many web users still manage to access the site via virtual proxy networks (VPNs).

A photograph of a pair of bare feet on a set of weighing scales indicating 97 kilograms (214 pounds) was among three pictures Ai also posted on the microblogging site, leading one punning follower to dub him "Ai Weighweigh."

The authorities have said the burly avant-garde artist, an outspoken critic of the Chinese Communist Party, was detained for tax evasion.

Rights groups have however said the outspoken 54-year-old, who is known for his fierce criticism of the ruling Communist Party, was detained as part of a wider clampdown on activists launched in February.

The government said he was freed on June 22 because of his "good attitude" in admitting to the charges against him, his willingness to repay taxes he owes and on medical grounds. He has diabetes.

Little has emerged about the conditions of Ai's three-month incarceration and the artist has said he is not allowed to give media interviews or leave Beijing without official permission as part of his bail conditions.

Ai last month accepted a job at Berlin University of the Arts.

"I hope to be able to contribute something important in the future," Ai said at the time, adding however it was "not clear" when he would be able to leave China and go to Berlin.

The Berlin university offered Ai the teaching position soon after his detention, saying it "stood for the freedom of the arts and therefore for the freedom of artists."

Chinese authorities have charged Beijing Fake Cultural Development Ltd., a design firm they say is "controlled" by Ai, with evading "a huge amount of taxes".