A Cheetah helicopter of the Indian Army crashed during a routine sortie on Wednesday morning in a forward area along the China border in Arunachal Pradesh, killing one of its two pilots.

The crash took place in the Jemeithang circle of Tawang district bordering China, which considers the frontier state to be a part of South Tibet. Tawang is one of India’s last points on the China frontier.

“An army aviation Cheetah helicopter flying in the forward area near Tawang has crashed around 10am during a routine sortie. Both the pilots were evacuated to the nearest military hospital. With regret we inform that one of the pilots who was critically injured succumbed to the injuries during treatment,” the army said in a statement.

The second pilot is undergoing treatment. The army has not revealed the cause of the crash. “Details are being ascertained,” the statement said.

The crash site is about 15km from the LAC and about 85km from district headquarters Tawang, sources said, adding the army was conducting its annual exercise in the Tawang area.

It is not known whether the chopper was part of the army exercise. It crashed while returning to Tawang from the BTK waterfalls under the Jemeithang circle, the last administrative centre bordering China.

Arunachal chief minister Pema Khandu, who hails from Tawang district, tweeted: “Pained by the news of crash of @adgpi helicopter at Nyamjang Chu near BTK area of Jemeithang circle in Tawang district. I am in touch with the Army officials for every possible assistance, and pray for speedy recovery of the injured pilots.”

Pema Khandu’s father, late chief minister Dorjee Khandu, died in a chopper crash in 2011 in the mountainous state, which remains a challenge for even the most experienced pilots because of sudden changes in weather and strong winds.

At least eight crashes have taken places in Arunachal Pradesh since 2010. An MI-17 chopper crashed in Anjaw district last year but there was no loss of life.

Another Cheetah chopper of the army had crashed in March this year near the Line of Control with Pakistan in Jammu and Kashmir. The pilot died while the co-pilot was severely injured.

In December last year India’s first chief of defence staff, Gen. Bipin Rawat, his wife and 12 defence forces personnel died when the Indian Air Force’s Mi-17V5 chopper crashed in Tamil Nadu.