Chinese artist and government critic Ai Weiwei is being pursued for nearly $2 million (£1.24 million) in unpaid taxes and fines.

Mr Ai is barred from speaking publicly after being released on bail last week from nearly three months in prison. But his friend Liu Xiaoyuan said Beijing’s tax office had issued a notice to Mr Ai that he owed the money.

Mr Liu said he had seen the notice and that Mr Ai had three days to respond to it in writing if he objects. Mr is the most high-profile target of a sweeping crackdown on activists this year.

Mr Ai’s family has denied he evaded any taxes and activists have denounced the accusation as a false premise for detaining him.

Chinese authorities sometimes try to silence critics by accusing them of tax violations or other non-political crimes.

Mr Ai, who has shown his work in London, New York and Berlin, has earned huge sums at auctions and through galleries. Last year he filled the Turbine Hall of London’s Tate Modern art gallery with millions of handmade porcelain sunflower seeds.

A 100-kilogram pile of the seeds sold for more than $550,000 (£343,000) at a Sotheby’s auction in February. Mr Ai’s mother, Gao Ying, said two tax bureau officials delivered the notice on Monday and asked him to sign it in acknowledgement but he refused.