Renowned Chinese artist and activist Ai Weiwei has been released on bail after confessing to tax evasion following more than three months in detention, China's state media reports.

Ai's poor health was also a factor in his release, the Xinhua News Agency reported.

It said Ai had shown a "good attitude in confessing his crimes" and repeatedly pledged to pay taxes he owed.

Xinhua repeated earlier allegations in state media that a company linked to Ai, Beijing Fake Cultural Development Ltd, had evaded a "huge amount" of taxes and intentionally destroyed accounting documents.