A Chinese-born American geologist has been released after seven years in a Chinese prison and returned home to Houston, a human-rights group said Saturday.

Xue Feng was released after serving all but 10 months of an eight-year sentence for "illegally procuring state secrets," a charge that foreign officials, scholars, and human-rights groups often cite as a political tactic for silencing government critics.

At the time of his release, Xue was the only American citizen serving a sentence in a Chinese prison on charges of endangering state security, according to the Dui Hua Foundation, a U.S.-based rights group that announced his release. - Deutsche Presse-Agentur