A senior Indian Air Force officer who was the sole survivor of last week's horrific chopper crash that claimed the lives of the country's first military chief and 12 others, died of his injuries on Wednesday.

Chief of Defence Staff General Bipin Rawat was on his way to Defence Services Staff College in Wellington when the Mi-17 V5 chopper crashed in the hilly terrain of the Nilgiris in the southern state of Tamil Nadu and burst into flames last Wednesday. 

Of the 14 people on board, 13 were charred to death. Air Force Group Captain Varun Singh was the only one to survive the crash, and had been on life support at a military hospital in the neighbouring southern state of Karnataka's capital Bengaluru.

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"The IAF is deeply saddened to inform the passing away of braveheart Group Captain Varun Singh, who succumbed this morning to the injuries sustained in the helicopter accident on 08 Dec 21. IAF offers sincere condolences and stands firmly with the bereaved family," it said in a statement.

Indian Prime Minister Narendra Modi took to Twitter to condole the Air Force officer's death.

"Group Captain Varun Singh served the nation with pride, valour and utmost professionalism. I am extremely anguished by his passing away. His rich service to the nation will never be forgotten. Condolences to his family and friends," he wrote.

A day after the crash, the Indian government ordered a tri-services investigation -- a probe by the Army, the Navy, and the Air Force -- into the chopper crash.

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Rawat, a four-star General, has had a chequered career in the armed forces spanning over 40 years, rising from the rank of a junior commissioned officer to the Indian Army chief and eventually the first head of the tri-services. He reported directly to the Indian Prime Minister.