Washington (AFP) - Chinese rights lawyer Gao Zhisheng suffered malnutrition and psychological abuse in prison, his wife said Wednesday as she called for Beijing to let him seek treatment in the United States.

Gao -- who has defended some of China's most vulnerable people such as underground Christians, aggrieved miners and members of the banned Falungong spiritual movement -- was released last week after serving a three-year prison sentence.

His wife, who fled with their two children to the United States in 2009, said that she has learned that Gao lost 22.5 kilograms (50 pounds) after being fed only a slice of bread and cabbage each day.

Gao can no longer speak intelligibly after being deprived of any interaction with people and kept in a small cell with little light and no reading material or television, she said.

"I am completely devastated by what the Chinese government has done to my husband. The only thing I feared more than him being killed was his suffering relentless and horrific torture and being kept alive," the wife, Geng He, said in a statement.

Gao remains under round-the-clock surveillance of Chinese authorities at his sister-in-law's home in the western Xinjiang region, where he was imprisoned, according to Freedom Now, a rights group that is offering him free legal representation.

Saying that Gao has been prevented from seeing a doctor since his release, Geng urged the United States to press China to allow him to come to travel.

"If President Xi Jinping has any sense of decency or humanity, after crushing my husband both physically and psychologically, the least he could do is allow me as a devoted wife to care for him," Geng said.

Despite Gao's release, China still imprisons a number of high-profile critics including Liu Xiaobo, the writer and democracy advocate who won the Nobel Peace Prize.