Chinese authorities agreed Thursday to review a fine imposed on a firm linked to controversial artist Ai Weiwei, who has said the $2.4 million penalty is an effort by the government to stifle his activism.

"They have two months to review the case. If we are not satisfied with the results, we can bring the case to court," said Pu Zhiqiang, a lawyer for Fake Cultural Development Ltd, a firm founded by Ai but registered to his wife.

Ai -- whose activism has made him a thorn in the side of China's communist authorities -- disappeared into custody for 81 days last year as police rounded up dissidents and lawyers amid online calls for Arab-style protests in China.

Upon his release in June, the world-renown artist was charged with tax evasion linked to Fake Cultural Development Ltd.

The Beijing tax bureau subsequently issued a bill for 15 million yuan ($2.4 million) in alleged back taxes in November, giving the artist 15 days to pay it or hand over an 8.45 million yuan guarantee.

Ai was able to pay the guarantee -- needed by law to challenge the charge -- thanks to a huge wave of donations from supporters of his activism and art.

Then last week, Ai's lawyers handed in a 9,000-word document requesting the review, pointing out inconsistencies with the case, including unregulated police involvement in Ai's detention and violations of China's tax code.

On Thursday, the Beijing tax bureau notified Ai that the review request had been accepted, Pu told AFP.

"We hope that the tax bureau will earnestly review the case," he said.

The 54-year-old artist -- whose sunflower seeds installation was exhibited at London's Tate Modern last year -- denies the tax evasion charges and insists the case is a politically motivated attempt to silence his activism.

He has angered authorities with his investigation into the collapse of schools in the 2008 Sichuan earthquake and into a 2010 fire at a Shanghai high-rise that killed dozens.

The sunflower seeds exhibition is due to open in New York at the Mary Boone Gallery.