Image copyright AP Image caption Xue Feng has been freed after a series of diplomatic attempts to secure his release.

A US geologist convicted of spying in China has been freed and returned to America, a human rights group says.

Dr Xue Feng was arrested in 2007 and in 2010 was sentenced to eight years in prison for stealing state secrets.

The US-based Dui Hua foundation said Dr Xue, 50, had been released from Beijing's No 2 prison 10 months short of serving his full sentence, after a reduction for good behaviour.

The report of Dr Xue's release could not be independently confirmed.

The Dui Hua foundation, which campaigns for clemency and better treatment for detainees in China, said that the geologist had arrived home in the US city of Houston.

"Dui Hua is delighted that Dr Xue has finally been reunited with his family in America after a terrible ordeal," the San Francisco-based group's executive director, John Kamm, said in a press release.

Dr Xue was detained in 2007 after negotiating the sale of an oil industry database to his employers, a US consultancy company.

His conviction was upheld by a Beijing appeals court in February 2011, and in November 2012 he was granted a 10-month reduction in his sentence for good behaviour.

If confirmed, his release would leave no US citizens imprisoned in China on charges of selling state secrets.