BEIJING (AP) — An outspoken Chinese human rights lawyer who disappeared for two weeks and was allegedly being held by security forces at an unknown location has returned home, an international rights group said Tuesday.

Gao Zhisheng, who has described being tortured in the past by Chinese security officials, is currently safe after Western diplomats pressed China on his case, according to Human Rights Watch.

The New-York based group did not give any other details and said it was not immediately clear when Gao was let go.

Gao, a bold critic of China's civil rights lapses, disappeared on Jan. 19 and was "subsequently detained by Chinese security forces," according to a joint letter issued earlier Tuesday by Amnesty International, Human Rights Watch and Human Rights in China that expressed fears for his safety and called for his release.

The groups were "particularly concerned" about his disappearance because it appeared arbitrary and did not follow any apparent action on Gao's part, said Nicholas Bequelin, Asia researcher for Human Rights Watch. "It seemed to be an escalation in treatment by security forces," he said.

China has long been criticized for its violations of freedom of speech and religion and brutal repression of critics, and the U.N. Human Rights Council is set to review its rights record starting next week.

Gao, an attorney, has tackled cases involving property-rights violations, the banned Falun Gong spiritual movement and religious persecution from 2002-2006.

He was arrested in August 2006, convicted at a one-day trial and placed under house arrest. He was accused of subversion on the basis of nine articles posted on foreign Web sites, state media reported at the time.

In September 2007, he was again detained for several weeks after sending an open letter to the U.S. Congress denouncing China's human rights situation and detailing his and his family's harsh treatment by security forces.

He graphically described torture sessions he allegedly endured that involved severe beatings, electric shock to his genitals, and cigarettes held to his eyes.

Last November, the U.N. Committee Against Torture issued a report on China saying that it remained "deeply concerned about the continued allegations, corroborated by numerous Chinese legal sources, of routine and widespread use of torture and ill-treatment of suspects in police custody."