By Claire Doole in Geneva
The UN has called on China to investigate fully all allegations of torture and abolish administrative detention centres, where reports of mistreatment are rife.
The Chinese delegation dismissed the criticisms as groundless, saying they were based on unproven allegations.
Human rights groups say torture is prevalent throughout China, inflicted on political and criminal prisoners.
But the UN Committee against Torture's assessment was more moderate - it fell short of condemning China for widespread abuse.
However, it did express concern at continuing allegations of torture against Tibetans, and urged China to promptly investigate all complaints of mistreatment.
Prisoners from Tibet have been dying in custody
The committee also asked China to consider abolishing all forms of administrative detention centres, which operate outside the legal system.
Beatrice Laroche, of Human Rights Watch China, says it is highly unlikely Beijing will close them down.
She claimed that China detained more people in the administrative detention system, where there is no judicial control or access to lawyers, than in prisons.
Human-rights groups were disappointed by the tone of the UN committee's recommendations.
Human rights groups were disappointed
They said it should have criticised China for its policy of forced abortions and sterilizations of women who break the one-child policy, and that it should have expressed greater concern at the increasing number of Tibetan prisoners dying in custody.
China, for its part, rejected the committee's criticism, while inviting members to see conditions for themselves - an invitation that it has repeatedly withheld from the UN's special investigator on torture, who has called for unhindered access to China's prisons.