Chinese dissident Chen Guangcheng called on the United States on Friday to ensure his family in China would be treated fairly, saying his imprisoned nephew was not receiving proper medical care from Chinese authorities, whom he accused of “hooligan tactics.”

Chen, who made international headlines last year when he escaped house arrest and spent 20 hours on the run before finding refuge at the U.S. Embassy in Beijing, said his nephew was suffering from appendicitis and being treated only by a fellow inmate who had received some medical training.

“He’s not being given proper medical treatment or being taken to a medical facility outside the jail,” Chen told Reuters in an interview, speaking through an interpreter.

Chen, who was born blind and taught himself law, said China was using “ruffian, hooligan tactics to try and scare me into silence.”

He said his relatives had been increasingly harassed by Chinese authorities since mid-April, around the anniversary of his escape from 19 months of harsh house arrest in eastern Shandong province.

He said he was “extremely happy and very grateful” to learn of the State Department’s announcement on Thursday that Secretary of State John Kerry would raise the case of his nephew, Chen Kegui, with China. He said he had not been contacted by anyone at the department about the plan.

Kerry tried calling Chinese Foreign Minister Wang Yi to discuss Chen’s imprisoned nephew, but Wang was not available, the State Department said on Friday.

Chen’s nephew was charged after using knives to fend off local officials who burst into his home the day after Chen’s escape was discovered. He was sentenced to more than three years in jail in November after a trial Washington described as “deeply flawed.”

Chen said, “There’s not enough power behind closed-door diplomacy,” and that the United States needed “to strengthen their criticism of the Chinese government,”

“What I mean is at the moment the methods that the U.S. government may be using to bring up these matters with the Chinese government is clearly not enough, it’s too weak. What they need to do is strengthen their criticism of the Chinese government.”

Chen came to prominence by campaigning for farmers and disabled citizens and exposing forced abortions before he was placed under house arrest.

Chen’s older brother, Chen Guangfu, said this week that local authorities had harassed him repeatedly since mid-April by throwing rocks, bottles and dead poultry at his home in a village in Shandong province in retaliation for what they believed were Chen’s plans to visit Taiwan and Tibet.

Chen said on Friday he planned to visit supporters in Taiwan next month but had no plans to visit Tibet. He spoke with Reuters after giving a speech at the launch of a report into Chinese censorship by PEN International, an association of writers that advocates for freedom of expression.

Chen, who lives in New York with his wife and is studying law at New York University, said he hoped to return to China.

“Part of the issue is, if I go back, will I be able to leave at any time?” he said.