US-based rights group Physicians for Human Rights has said that Indian security forces used "indiscriminate" against protesters in Kashmir.
The group pointed to the use of shotguns that fired pellets, which caused injuries and blindness.
At least 90 people died and more than 1,500 others were injured in clashes earlier this year.
Protests broke out after security forces killed a well-known militant leader in July.
Burhan Wani, 22, died in a gunfight with the Indian army on 8 July.
The pellets - made of rubber-encased steel - are meant to be non-lethal but doctors say they have caused serious head and eye injuries in many victims.
Physicians for Human Rights said it interviewed doctors and injured protesters and reviewed hospital records.
The report said, "media reports, doctors working in Jammu and Kashmir, and civil society organisations monitoring the numbers of injuries and deaths reported that an estimated 12 to 15 deaths and an estimated 5,208 injuries could be attributed to the use of 12-gauge shotguns," which are also referred to as pellet guns.
It said shotguns fire cartridges containing more than 600 pellets - ammunition it described as "inherently indiscriminate and inaccurate" that should never be used against protesters.
"At close range, such weapons have the force of live ammunition. And at a distance, the pellets disperse and can take an unpredictable trajectory, meaning they can indiscriminately inflict severe injury on nonviolent protesters or bystanders, particularly when those pellets strike the head, neck, face, or eyes," the group's medical adviser, Dr Rohini Haar was quoted as saying by the Associated Press news agency.
Indian authorities have not yet reacted to the report.
Kashmir has been a flashpoint between India and Pakistan for more than 60 years, sparking two wars between the countries.
Within the Muslim-majority territory, some militant groups have taken up arms to fight for independence from Indian rule or a merger with Pakistan.