Detained rights activist Wu Gan, known by his online nickname "The Butcher," has suffered torture while being held under investigation in a police detention center in the northern port city of Tianjin, his lawyers have complained after visiting him last week. Wu Gan, 42, was initially detained in the eastern province of Jiangxi last year and handed a 10-day administrative sentence before being placed under criminal detention on suspicion of "picking quarrels and stirring up trouble," "libel," and "incitement to subvert state power." The "libel" charge was later dropped and his case transferred to Tianjin, making it likely that he is being treated as part of a nationwide crackdown on lawyers and rights activists that began July 9, 2015 with a raid on the Beijing Fengrui law firm. His lawyers Ge Yongxi and Yan Xin said he had been tortured following a meeting with Wu at the Tianjin No. 2 Detention Center. In a complaint filed to the Tianjin municipal state prosecutor's office, Yan wrote that Wu had been interrogated "more than 300 times" since his incarceration began. "Wu Gan has been subjected to illegal treatment during his detention," the complaint said. It said Wu had been repeatedly and illegally held in solitary confinement, tortured, and deprived of his right to complai and to access legal advice. The complaint called on the prosecutor's office to investigation the allegations, "to find out which departments and individuals are responsible." 'Nothing to add' Ge declined to comment when contacted by RFA recently, however. "I have already released the information I am able to release, and I have nothing else to add," he said. Calls to Yan Xin's phone rang unanswered on Sunday. A friend of Wu's, who asked to remain anonymous, said his treatment was in line with that meted out to other detainees in the crackdown on lawyers, including rights attorneys Li Heping and Wang Quanzhang. He said the fact that Wu had finally been allowed a visit from his lawyers suggests the authorities may have run out of ways to stall his case. "His case has been sent back for further investigation on a number of occasions, probably because he refuses to confess to the charges against him," the friend said. "They have now exhausted all the procedural options open to them under Chinese law, and on top of that, there is the pressure of international public opinion," he said. Torture widespread Guangdong-based rights activist Ye Du said the use of torture and other forms of mistreatment to elicit "confessions" from political detainees has become widespread for dissenting voices in China in recent years. "Pretty much all of the big political cases now use these methods on the victims," Ye said. "They have already had the trials of several others who were forced into making confessions." "It's easy to imagine the sorts of torment they must have been put through in order to[confess]," he said. "It says a lot that Wu Gan has been able to withstand it, and he deserves our respect for that," Ye said. Fellow rights activist Zhuang Lei said many people have been deeply angered by the reports of Wu's mistreatment in detention. "Civil society is very angry about this torture, which is a serious violation of someone's fundamental human rights," Zhuang said. Performance protest Wang was initially detained by police during a performance protest he titled "Selling my Body to Raise Funds" in Nanchang city in eastern Jiangxi province. He was trying to help finance a legal defense for Huang Zhiqiang, Fang Chunping, Cheng Fagen, and Cheng Lihe, who were jailed in Jiangxi's Leping city for robbery, rape, and dismembering a corpse. The four received suspended death sentences in 2000 that were later commuted to jail terms, but their lawyers and rights activists say their confessions were obtained through torture, and that the men are victims of a miscarriage of justice. Meanwhile, the official media has hit out at Wu for his criticism of the police shooting of a man at a railway station in the northeastern province of Heilongjiang in May 2015. Wu likely drew the ire of authorities by expressing doubts online over the credibility of the government's investigation of the killing, rights groups have said.