Ai Weiwei has gotten back his passport four years after it was confiscated by Chinese authorities and plans to attend a London exhibition this fall.

The artist and government critic posted an Instagram photo Wednesday of himself holding a Chinese passport with the caption, "Today, I got my passport."

Ai's representative confirmed the passport had been returned, but didn't immediately respond to further questions.

Ai was detained by authorities for about three months in 2011 but not charged. His design firm later was slapped with a $2.4 million tax bill, which he fought unsuccessfully in Chinese courts.

Chinese authorities often deny passports to dissidents who might embarrass the ruling Communist Party overseas.

Ai's work has gotten much attention worldwide, making him one of best-known Chinese dissidents.

Britain's Royal Academy of Arts said Ai would travel to London for a major exhibition of his work in September.

"This is wonderful news for Ai Weiwei, his family and for artists worldwide," said Royal Academy director Tim Marlow. "We are delighted to announce that he will be joining us as we finalize the installation of his exhibition."

Ai's work is very popular in Britain. In 2010 he filled a vast hall at the Tate Modern gallery with 100 million ceramic sunflower seeds. Visitors were initially invited to walk or lie on them, but after a few days the ceramic dust was judged a health hazard and the exhibit was cordoned off.

It still attracted large crowds.

Before his detention, Ai had spoken out about a number of national scandals, including the deaths of students in shoddily built schools that collapsed during a massive earthquake in 2008.

The government has blacklisted him from any mention in state media, and he is not allowed to post anything on China's social media.