The first U.N. torture investigator to visit China said Friday that abuse was still widespread and authorities subjected detainees to electric shocks, beatings and sleep deprivation. He also accused the government of obstructing his work.

Manfred Nowak, the U.N. Human Rights Commission's special investigator on torture, told reporters at the end of his trip that certain groups have been particular targets of torture: political dissidents, human rights activists, practitioners of Falun Gong, unofficial church groups and Tibetan and Uighur minorities.

Nowak's visit, which began Nov. 21, capped a decade-long effort by the U.N. to send an investigator to look into claims of torture and mistreatment by Chinese authorities. Beijing has repeatedly agreed to allow the visits and then postponed them.

When asked about the prevalence of torture, which was outlawed in 1996, Nowak replied: "I consider it on the decline but still widespread."

Nowak visited detention centers in Beijing, Tibet and the Muslim-majority region of Xinjiang, and held talks with top Chinese prosecutors and justice officials.

A United Nations statement said the organization has received reports that Chinese authorities, over the years, have used various methods of torture including electric shock batons, cigarettes, hoods or blindfolds, submerging prisoners in water or sewage or exposing them to extreme heat or cold.

Based on the information Nowak gathered, he was able to confirm that "many of these methods of torture have been used in China," the statement said.

"Very often an individual police officer is not instructed to torture but is under pressure to extract a confession," he told reporters.

Nowak also complained that Chinese security agents attempted at various times throughout the visit to obstruct or restrict his attempts at fact-finding.

"There was frequent surveillance of my interviews that I had outside the prisons with victim's family members by intelligence agents who tried to on the one hand to listen to our private conversations," Nowak said.

In addition, "victim's families were actually prevented by various means, by putting them under house arrest, or physically prevented them, from coming to meet me."

Nowak, a Vienna law professor, said he was prevented from bringing photographic and electronic equipment into prisons.

The U.N. has received a significant number of complaints that political dissidents, human rights defenders, practitioners of Falun Gong, members of unofficial church groups and Tibetans and Uighurs have been victims of "a consistent and systematic pattern of torture," the statement said.

Those groups have all been branded as subversive by China's ruling Communist Party and are frequently detained, imprisoned and sent to "re-education" labor camps.

"Re-education through labor and similar measures of forced re-education in prisons, pretrial detention centers and psychiatric hospitals should ... be abolished," Nowak's statement said.

Human rights groups say many people from those groups are tortured to death. Authorities usually tell relatives they died of natural causes or committed suicide.

Nowak urged China to further develop its criminal system to encourage fair trials and ensure that dissidents and other groups are not imprisoned under vaguely worded state security laws.

"Many steps need to be taken to build up a system that respects the rule of law," he said.

Nowak said he met with about 30 people in detention, but could not give details on many of them because they spoke to him on condition of anonymity.

He brought up the case of He Depu, a dissident serving a prison sentence for subversion after he was arrested for signing a letter to Communist Party delegates urging political reforms.

Nowak said he was subjected to 85 days of torture, including being forced to stay in one position and not being allowed to sleep. "It breaks you," Nowak said.

One case that provoked rare discussion of the topic in state-controlled media centered on a man in central China who was released in April after 11 years in prison when his wife, whom he had been accused of murdering, turned up alive.

She Xianglin said that for 10 days and nights he denied killing his wife. But police kept him awake, interrogating him almost constantly, until finally the former security guard signed a confession that he says he didn't even read.

Nowak will include his findings in a report to be submitted at next year's meeting of the U.N. Human Rights Commission.