Demonstrators cast their shadows onto a Chinese national flag during a protest outside the Japanese embassy in Beijing September 14, 2012. REUTERS/David Gray LILING, China (AP) — The local Chinese official remembers the panic he felt in Room 109. He had refused to confess to bribery he says he didn't commit, and his Communist Party interrogators were forcing his legs apart.

Zhou Wangyan heard his left thigh bone snap, with a loud "ka-cha." The sound nearly drowned out his howls of pain.

"My leg is broken," Zhou told the interrogators. According to Zhou, they ignored his pleas.

China's government is under strong pressure to fight rampant corruption in its ranks, faced with the anger of an increasingly prosperous, well-educated and Internet-savvy public.

However, the party's methods for extracting confessions expose its 85 million members and their families to the risk of abuse. Experts estimate at least several thousand people are secretly detained every year for weeks or months under an internal system that is separate from state justice.

In a rare display of public defiance, Zhou and three other party members in Hunan described to The Associated Press the months of abuse they endured less than two years ago, in separate cases, while in detention. Zhou, land bureau director for the city of Liling, said he was deprived of sleep and food, nearly drowned, whipped with wires and forced to eat excrement. The others reported being turned into human punching bags, strung up by the wrists from high windows, or dragged along the floor, face down, by their feet.

All said they talked to The Associated Press despite the risk of retaliation because they were victims of political vendettas and wanted to expose what had happened. Party officials denied any abuses had taken place.

Zhou's account is supported by medical records, prosecutor statements, party reports and a notice confirming that police failed to investigate the abuse. The AP also corroborated information through interviews with family and friends.

A Liling party official named Yi Dingfeng said provincial authorities were investigating the case. Local anti-graft officials on a Hunan online forum in February last year denied Zhou was tortured, saying he injured himself by slipping in the bathroom.

Eighteen months after his leg broke, Zhou still limps on crutches.

"My time in shuanggui was tragic and brutal. It was a living hell," he says. "Those 184 days and five hours were not a life lived by a human. It was worse than being a pig or a dog."

The abuse of suspects in China is hardly limited to party members. And critics say President Xi Jinping is clamping down even more strongly on society than his predecessor, with increased detentions of people who push for political change, protest censorship and demand that officials disclose their wealth.

However, little is known or reported about mistreatment within the party's obscure detention system for its own members.

Chinese laws say only prosecutors and police have the right to arrest or detain people. Party experts acknowledge their internal detention system is legally problematic, but say it is essential because party members often control the courts and police. A party official said 90 percent of major corruption cases in recent years were cracked through secret detention.

Aside from Zhou, three others told the AP about their detention. Wang Qiuping, a party secretary in Ningyuan, said he was slapped often and forced to stand and kneel for hours during a detention of 313 days. His deputy Xiao Yifei told the AP he was hooded for more than a month and beaten by an interrogator who went by the nickname "Tang the Butcher."

And Fan Qiqing, a contractor, said he was kicked, lashed and forced to take hallucinogenic drugs. A Ningyuan party official said only that the investigation involving the three men was carried out in a "civilized manner" and no one was tortured.

Zhou, then 47, was taken away from his office in July 2012 by three men from the party's local anti-graft agency. He blames his detention on a party boss who bore him a grudge, later removed by the party in an investigation without reasons given.

Zhou spent most of his six months of detention at Qiaotoubao, known as a model center for anti-corruption efforts. The local government conducts regular tours of Qiaotoubao to warn party cadres against corruption. On an official tour in 2011, Zhou himself had noted the audio and video surveillance in each room and concluded that it seemed like "a safe environment" for detainees.

In Qiaotoubao, Zhou's questioners punched him and dragged him on the floor by his hair, he says. They made him smoke 10 cigarettes at once with his face near lit coals. They pressed his face into water in a sink until he thought he was drowning. They slapped his face with shoes and broke four teeth.

On at least three nights, they pinned him down and force-fed him feces and urine with a spoon. They dubbed the meals "American Western Feast" and "Eight Treasures Porridge."

Most painful of all, they showed him a video of his 22-year-old daughter being detained for 48 hours and interrogated.

It was in September that the interrogators broke his leg. Two weeks later, Zhou started slipping into unconsciousness. Only then, he says, did they let him go to a hospital under the false name of Wang Yan, with the story that he had fallen in the bathroom.

Medical records show that upon admission to the Zhuzhou City No. 1 People's Hospital on Sept. 29, his thighs, calves and feet were swollen, his skin red and hot and his left thigh badly bruised. Further tests revealed fluid in his thighs, kidney stones, an enlarged liver and swollen lymph nodes on his groin. Scans confirmed that his left thigh had broken into several pieces.

A week after surgery, Zhou's investigators took him back to Room 109, he says.

It was three months later, in the winter, when Zhou finally caved. He signed a confession saying he had accepted 40,000 yuan, or $6,600, in bribes and wrote a resignation letter.

He was released in January last year. An amateur video shot that day by his family shows a visibly thinner Zhou hobbling out of the building on crutches. He was helped on a stretcher and into an ambulance.

A week later, Zhou submitted complaints to party and provincial authorities. In November, prosecutors decided not to indict Zhou, according to a notice from the Liling City Procuratorate.

A year after Zhou's release, no action has been taken against his interrogators. Strict censorship rules prevent Chinese state media from reporting on the case, so Zhou says he is taking the tremendous risk of talking to the foreign media.

Since the AP contacted Communist Party officials for comment, Zhou has received two calls warning him not to talk. Wang, his wife and his younger brother got similar calls threatening "consequences," and Wang was told he would no longer receive a salary or health insurance.

Despite everything, Zhou hopes for justice.

"I still believe that the Chinese Communist Party is a good ruling party," Zhou says. "I also believe that not too far in the future, there will be a place in the People's Republic of China in which we can speak freely, a place where my terrible case will receive a fair and just response."

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Follow Gillian Wong on Twitter at twitter.com/gillianwong