The wife of prominent Chinese artist-activist Ai Weiwei was taken away by police for three hours of questioning on Tuesday, Ai said, adding that he still had not spoken to his wife Lu Qing about the reasons for the renewed scrutiny from authorities.

She was taken away for questioning, and then she was released about half an hour ago, Ai told Reuters.

I haven't had a chance to speak to her so I'm not sure about the circumstances.

Ai, whose 81-day secret detention ignited an international uproar, was released in late June. Ai and his supporters said he was the victim of the ruling Communist Party's crackdown on dissent. The government accused him of tax evasion, a charged he denied.

Ai, who had a hand in designing the Bird's Nest stadium for the 2008 Beijing Olympics, paid a bond of 8.45 million yuan ($1.3 million) this month, paving the way to file an appeal against the tax evasion charge.

The money was raised from contributions from his supporters.

Ai has said his wife is the legally-registered representative of the company at the heart of the tax dispute, and therefore could also be targeted in the charges.

($1 = 6.354 Chinese yuan)

(Reporting by Chris Buckley; Editing by Yoko Nishikawa)