The International Committee of the Red Cross sent evidence to US diplomats about widespread torture by Indian security forces in Kashmir, according to cables obtained by Wikileaks.
Visits to detention centres in the region in 2002-04 revealed cases of beatings, electric shocks, sexual abuse and other types of ill-treatment.
The organisation concluded that India condoned torture in the region.
There has been no comment from the US. The ICRC said it was investigating.
The chief minister of the state of Jammu and Kashmir, Omar Abdullah, told India's NDTV channel that the allegations related to a period before his government took power and that he did not condone torture.
Correspondents say the revelations will be embarrassing for Delhi, coming at a time of heightened sensitivity in Kashmir, which is divided between Indian and Pakistani control.
They were published by The Guardian newspaper in the UK, one of five publications - including the New York Times, France's Le Monde, El Pais in Spain and Germany's Der Spiegel - given access to the entire archive of the reports from US diplomats out in the field by Wikileaks.
Wikileaks website says it has obtained more than 250,000 cables passed between the US State Department and hundreds of American diplomatic outposts - but it has so far only published a small sample of those messages.
The site's founder, Julian Assange, was on Thursday freed on bail in London, where he is fighting extradition to Sweden over sex assault allegations made by two women. He denies any wrongdoing. BBC News
