Official sources said the choppers, which returned to the Chinese side after about five minutes, could have carried out aerial photography of Indian ground troops during what was possibly a reconnaissance mission.
The Indian Air Force (IAF) is probing the incident, an IAF source said.
The choppers were identified as the Zhiba series of attack helicopters.
On previous occasions, Chinese helicopters had entered 4.5 kilometres into Indian territory, an area that China claims as its own and recognises as Wu-Je.
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Barahoti is one of three border posts in the sector, comprising Uttar Pradesh, Himachal Pradesh and Uttarakhand, where ITBP jawans are not allowed to carry weapons and are in civilian clothes under a unilateral decision taken by the Central government in June 2000.
In 1958, India and China listed Barahoti, an 80-sq-km sloping pasture, as a disputed area where neither side would send their troops. In the 1962 India-China war, the PLA did not enter the 545-km middle sector, focusing on the Western (Ladakh) and Eastern (Arunachal Pradesh) sectors.
During prolonged negotiations on resolving border disputes, the Indian side had unilaterally decided in June 2000 that ITBP troops would not be carrying arms to three posts -- Barahoti, Kauril and Shipki in Himachal Pradesh.
Srikanth Kondapalli, Professor in Chinese Studies at the Jawaharlal Nehru University, termed these transgression as "testing the nerves" of India and said "after violating the Line of Actual Control in the Western and Eastern sectors, Chinese troops now seem to be focusing on the middle sector. It's a cause of worry for us".
"But that didn't happen. Today the PAPF (People's Armed Paramilitary Force) and PLA are enforcing China's claims there," he said.
Kondapalli referred to regional equations giving a China a boost. He recalled that Nepal and India had differences on the source of the Mahakali river and in the background of China's forays in Nepal as well as the latter joining the China-led One Belt One Road (OBOR) project, and said, "There have been some moves by the PLA to test us".
"So the latest intrusion is to test our nerves," he said.
He even said China could deploy Unmanned Aerial Vehicles in this region in "large numbers" to monitor Indian territory.
"So the helicopter incident is a precursor," he said. "A recce mission?"
Security officials here felt that ahead of its transgression in the Barahoti area, the PLA could have conducted a reconnaissance mission using high class aircraft with Synthetic Aperture Radar (SAR), which provides broad-area imaging at high resolutions.
They said there was a possibility that the same aircraft, designed by Chinese companies on the basis of technology obtained from the former Soviet Union, could have been used this year, too.
The aircraft flies at an altitude of above 40,000 feet and can go up to 60,000 feet to avoid detection by radars and can take photographs and cyber and communication signatures from that height.
SAR enables the taking of high-resolution pictures even in inclement weather or in the dark.
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