According to the Chinese state media, an Indian drone "invaded China's airspace and crashed" on its territory.
Zhang Shuili, deputy director of the western theatre combat bureau, said that the incident took place in "recent days". He did not give an exact location.
He was quoted in Xinhua news agency as saying that India had "violated China's territorial sovereignty".
According to the Indian army, the drone had been deployed on a training mission and developed a technical problem.
He added that China expresses "our strong dissatisfaction and opposition regarding this matter" and that it would "steadfastly protect the country's rights and safety".