Chinese dissident artist Ai Weiwei was flying to Germany Thursday on his first overseas trip since he was arrested nearly four years ago, a week after receiving a new passport.

Ai was expected to arrive on a Lufthansa flight to the southern city of Munich at 1450 GMT, Stephan Urbaschek of his Berlin gallery, Galerie Neugerriemschneider, told AFP.

"We are overjoyed," Urbaschek said, adding that it was extraordinary news that "the incomprehensible travel restriction" against Ai had been lifted.

In the comings days, 57-year-old Ai was expected to travel on to the German capital Berlin where his six-year-old son lives, said Urbaschek.

China's best known contemporary artist, Ai was detained for 81 days in 2011 amid a crackdown on government critics, but not formally charged with any crime.

A company run by his wife and listing him as an employee was fined $2.4 million the following year after losing a civil legal battle against tax authorities, proceedings widely seen as a reprisal for Ai's outspoken criticism of the ruling Communist party.

Authorities in 2011 confiscated Ai's passport, but police returned the document earlier this month.

Ai said last week that Germany had granted him a four-year multiple entry visa.

Earlier Thursday Ai revealed that Britain has denied him a six-month visa and restricted him to a three-week trip, with the embassy claiming he had failed to declare a "criminal conviction" in his application.

Ai said in a separate Instagram post he had "never been charged or convicted of a crime", while the British decision prompted outrage online and condemnation from rights groups.

The visa he was granted would ensure that Ai can attend a show of his work at London's Royal Academy of Arts in September but he will not be in Britain in October when China's President Xi Jinping pays a high-profile state visit.

Ai helped to design the Bird's Nest Olympic Stadium for the 2008 Beijing Games, but the burly artist's criticism of China's leaders has made him a thorn in the government's side.