The lawyer and relatives of a rights activist from the southern province of Guangdong who died in police custody earlier this month said on Tuesday his body shows multiple signs of severe physical assault.
The report comes as Chinese officials were questioned at the United Nations by officials reviewing Beijing's record on torture.
Zhang Liumao was reported dead by authorities in the Guangzhou No. 3 Detention Center in the early hours of Nov. 4, prompting suspicions from his family that he was tortured.
"The family [viewed the body] so as to confirm that it was Zhang Liumao, while I went as their lawyer mainly to see if there were any problems evident on his body," lawyer Tan Chenshou told RFA after the identification process.
"There was a good deal of bruising all over his body, including his abdominal area, which was black and blue all over," Tan told RFA.
"The most serious injuries seemed to be around his chest, where there were rectangular marks and curved bloodied areas, and there was some swelling around his elbow and a very swollen area on his arm, which suggest perhaps a broken bone or something like that," he said.
"There were ... some flesh wounds, as well as some older scars," Tan said, adding that he will now check the scarring and signs of injury against records of the routine medical check at the time of Zhang's detention.
Zhang had been charged with "picking quarrels and stirring up trouble," a public order charge often used to target critics of the government, but was later reported dead with no explanation offered to the family by detention center staff.
His sister Zhang Wuzhou said relatives were prevented from taking cell phones or cameras to identify her brother's body.
But she said she is certain that Zhang was "beaten to death" while in detention.
"He was killed, beaten to death by them as they tried to force a confession from him," she said. "This is very hard for me to take; it is so cruel."
She added: "He was clearly tortured; there are so many things that arouse suspicion. I have demanded that they tell us the truth, but we haven't heard it yet."
Zhang Wuzhou said her sister Zhang Weichu is in the process of taking legal advice.
"But can we even rely on the law, now that hundreds of Chinese lawyers have been detained?" she said.
Zhang Wuzhou said the family is also mistrustful of anyone who carries out an official autopsy on Zhang's body.
"They wanted an autopsy to be carried out ... by a medical examiner from Guangzhou police department," she said. "But they are the ones who have broken the law, so we refused to allow it."
"We still have questions about my brother's death."
The suspicions surrounding Zhang's death came as U.N. rights experts pressed senior Chinese officials on Tuesday about persistent allegations that torture is rife in their police stations and prisons, especially of political prisoners, and about deaths in custody.
Chinese officials said they are working to combat torture, while admitting that it hasn't been eliminated.
The United Nations Committee Against Torture will continue to review Beijing's implementation of the Convention against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment in Geneva on Wednesday.
Rights groups say Beijing has prevented a number of activists from traveling to Geneva to give evidence to the committee, however.
However, a Hong Kong delegation, including Human Rights Monitor director Law Yuk-kai, did attend.
"We will be reporting on police ... use of excessive force, especially during the Umbrella Movement," Law told RFA, in a reference to last year's pro-democracy movement in the former British colony.
"All vulnerable groups have expressed concern, including the disabled, women, LGBT and refugees," he said. "They have reported inhumane treatment, domestic violence and sexual violence and various policies that aren't in their interests."
New York-based Human Rights Watch has accused the Chinese authorities of showing "cruel disregard" for the health of prisoners of conscience, citing the deaths in custody of rights activist Cao Shunli and popular Tibetan monk Tenzin Delek Rinpoche.
Campaign group Free Tibet and its research partner Tibet Watch gave evidence to the committee including graphic testimonies from torture survivors, reports of deaths in custody as a result of torture and details of degradation, abuse and mental and physical torture that continue to be faced by Tibetan prisoners.
China was last reviewed by the committee in 2008, when it found torture across China and Tibet to be “widespread” and “routine” and expressed “great concern” about reported torture and state violence in Tibet, the group said in a press release on Tuesday.
The New York-based group Human Rights in China says the past year has been "a year of massive crackdowns on rights activists and lawyers" on the mainland.
And Amnesty International said in a report last week that China's criminal justice system relies heavily on forced confessions obtained through torture, including beatings and the use of iron restraint chairs, with dissidents and minorities at the highest risk.
It said defense lawyers who complain of torture and forced confessions are threatened, detained or even tortured, citing the ongoing detention of 12 Chinese rights lawyers and legal activists on state security charges.
Reported by Yang Fan for RFA's Mandarin Service, and by Lo Man-san for the Cantonese Service. Translated and written in English by Luisetta Mudie.