The UK has granted a six-month business visa to dissident Chinese artist Ai Weiwei after initially rejecting his application over an alleged criminal conviction.

Britain's interior ministry said on Friday that Theresa May, the head of the ministry, had looked into the case and instructed officials to grant the visa.

The ministry said it had written to Ai "apologizing for the inconvenience caused".

On Thursday, the renowned activist disclosed that the British embassy in Beijing had turned down his request for a business visa, saying he had failed to disclose a criminal conviction.

Instead it gave him a visa covering 20 days in September, when a major exhibition of Ai's work is opening at London's Royal Academy.

Ai, who often uses his work to draw attention to corruption and injustices in Chinese society, was detained for almost three months in 2011 amid a wider crackdown on dissent in China.

His company was later accused of tax evasion and ordered to pay $2.4m. However, Ai's lawyer said he had never been charged or convicted of a crime in China.

After his release from prison in 2011, Ai was placed under a travel ban that was only fully lifted when his passport was returned last week. On Thursday, he flew to Germany, where members of his family live.