Nearly 2,600 bodies have been discovered in single, unmarked graves and in mass graves throughout mountainous Indian-controlled Kashmir, a human rights group said Wednesday. More than a dozen Kashmiri rebel groups have been fighting for independence from India or for a union with Pakistan since 1989. Rights groups say more than 8,000 people have disappeared since the rebellion began and the groups have for years accused the government of killing innocent civilians as well as militants.

Researchers from the International People’s Tribunal on Human Rights and Justice, a rights group in Indian-held Kashmir, said they found the graves during a three-year survey that concluded last month. Indian officials have said in the past that many militants have been killed in fighting with security forces and that their bodies are often buried in unmarked graves. “We’re not saying who is in each grave,” said Angna Chatterji, one of the members of the rights group. “But we’re saying these are unnamed graves and it’s imperative to investigate the issue by an independent international body.”