The Ministry of Defence on Thursday said a drone operated by Indian security forces in Sikkim had crossed over the Line of Actual Control with China during a training mission, after it lost contact with ground control because of a technical problem.

The statement came after the People’s Liberation Army of China “voiced strong dissatisfaction and opposition to the intrusion of an Indian unmanned aerial vehicle into China’s airspace”, Xinhua reported.

“As per standard protocol, the Indian border security personnel immediately alerted their Chinese counterparts to locate the UAV,” the Defence Ministry said. “In response, the Chinese side reverted with the location details of the UAV.”

Zhang Shuili, deputy head of the combat bureau of China’s Western Theater Command’s joint staff department, said, “India’s move has infringed upon China’s territorial sovereignty, and we are strongly dissatisfied with and opposed to this.”

The Xinhua report did not mention details of when or where the drone ventured across the Sino-Indian border. It also did not specify what markings led China to believe that the unmanned aerial vehicle was from India.

This comes about two months after India and China ended their 74-day military standoff in the Sikkim sector’s Doklam region. Beijing and New Delhi had both maintained that troops from the other nation had transgressed into their territory. The standoff began and strained bilateral ties after the Indian Army stopped China from constructing a road in Doklam.