Torture of suspects in police detention is widespread in China, Amnesty International said Thursday, citing interviews with nearly 40 lawyers, some of whom said they themselves had been beaten while attempting to protect their clients.

Suspects received electric shocks, were punched, kicked, hit with shoes or bottles filled with water, denied sleep and locked in iron chairs forcing them into painful postures for hours on end, the rights group said.

The report, echoing findings by journalists and other rights groups, comes a week before China's record is set to be scrutinised by the United Nations' anti-torture committee.

It cited official data as saying that China's top prosecutorial body received at least 1,321 reports of "extracting confession through torture" from 2008 to the first half of 2015.

But just 279 individuals were convicted of the offence over the same period, the British-based group added.

"For the police, obtaining a confession is still the easiest way to secure a conviction," said Amnesty researcher Patrick Poon.

"The government seems more concerned about the potential embarrassment wrongful convictions can cause than about curbing torture in detention," he added.

Fewer than 20 percent of criminal suspects in China have access to lawyers, the group said, making abuses harder to prevent.

Some lawyers representing activists or members of banned religious groups have themselves ended up being tortured, it added.

Beijing lawyer Yu Wensheng said his wrists were shackled behind his back with painfully tight handcuffs during a near 100-day detention in 2014.

"My hands were swollen and I felt so much pain that I didn't want to live. The police officers repeatedly yanked the handcuffs and I would scream," Amnesty cited him as saying.

The group mostly spoke to attorneys who specialise in sensitive rights cases, and who the ruling Communist Party see as political opponents.

Of the 37 lawyers the group interviewed, 10 experienced torture or other ill-treatment themselves in incidents dating back to 2010.

Courts regularly admit evidence which has allegedly been extracted by torture, the group said, citing a sample of 590 cases in which allegations of torture were made -- with the "confessions" excluded in just 16 of them.

- 'Fairness and justice' -

Chinese officials often say that Amnesty is "biased" against them.

China says it is taking measures to reduce the prevalence of forced confessions, including installing cameras in interrogation rooms and adopting laws banning the practice.

"Chinese law clearly prohibits the practice of forced confession in interrogation", foreign ministry spokesman Hong Lei told a regular briefing Thursday.

"We will continue to improve our system of human rights and judicial protection so that everyone will be treated with fairness and justice."

But Amnesty said that Chinese prosecutors and courts are controlled by Communist Party officials who tend to side with the police, limiting the impact of such reforms.

"Local officials and police continue to pull the strings of China's criminal justice system. Despite defence lawyers' best efforts, many claims of torture are simply ignored," Poon said.

China signed up to the United Nations Convention against Torture in 1986 and a periodic review of its record will be held in Geneva next week.

US-based Human Rights Watch's China director Sophie Richardson said in a statement ahead of the hearings: "Torture remains a daily reality in China, and this is a critical moment for Beijing to answer tough questions about why this problem persists."