China has ordered Ai Weiwei to pay 15 million yuan ($2.2 million) in back taxes and fines allegedly due from the company he works for, the dissident artist said.

Supporters say the case is part of Beijing's efforts to muzzle government critics.

The 54-year-old artist, famous for his work on the Bird's Nest Olympic Stadium in Beijing, was detained without charge for 81 days this year in a move that drew criticism from Western governments.

Ai, who was released in late June, said he received the notice from the tax authorities that described his title as the "actual controller" for Beijing Fake Cultural Development Ltd, which has helped produce Ai's internationally renowned art and designs.

The company is owned by his wife, Lu Qing, who is the firm's legal representative.

"They made up this new title," Ai said.

"I'm a designer for the company. I'm not a director, or even a manager. Of course, I know this matter is targeted at me.

"They said: 'We're fining the company, not you.' But I said: 'Why was my name singled out by the government, at the foreign ministry briefings?'

"But they still said to me: 'This has nothing to do with you'."

Rights activists said the charges were a pretext for silencing the artist who has been a fierce government critic.

"It appears that the government is set to destroy him, if not economically then at least by setting up the stage to later arrest him for failing to pay back taxes," said Songlian Wang, research coordinator for Chinese Human Rights Defenders.

Ai said he had not received any evidence of tax evasion, adding that he did not believe the company had evaded payment.

"Up till this day, Fake Company has not seen any account statements," Ai said.

"I told them: 'This is not reasonable.'

"But they told me: 'If the country says you have evaded taxes, then you must have evaded them. Why don't you lose hope? This country will never change its ways'."

The Beijing Local Taxation Bureau told Ai he had to pay about 5.3 million yuan in back taxes, 6.8 million yuan in fines and about 3 million yuan in late payments. Calls to the bureau went unanswered.

'This is ridiculous'

Ai said he had been given 15 days to pay up.

"If it's a tax problem, I'll pay. But if it's not, I won't pay," Ai said.

"This whole matter is ridiculous."

Beijing authorities held a closed tax evasion hearing in July. The company's lawyer, Pu Zhiqiang, said it was illegal for them to do so.

Ai was barred from attending, but his wife, Lu, was present.

He tweeted on Tuesday that the authorities had threatened the company's accountant and manager and prevented them from meeting him.

Ai was detained at Beijing airport on April 3, prompting an outcry about China's tightening grip on dissent which has seen the detention of dozens of rights activists and dissidents.

The bearded, burly artist was the most internationally acclaimed of those detained, and his family has repeatedly said he was targeted for his outspoken criticism of censorship and Communist Party controls.

When Ai was released on bail in June, the government said he remained under investigation on suspicion of economic crimes.

Ai previously said that he had not received a formal notice to explain "suspected economic crimes".

Under the conditions of his release, Ai was told by the authorities he was not allowed to speak to foreign media, post messages on Twitter or leave Beijing for a year.

Reuters