The only survivor of a helicopter crash that killed India"s top military official has died from his injuries after nearly a week on life support, the Indian Air Force (IAF) said in a statement Wednesday. Group Capt. Varun Singh was in the helicopter with India"s Chief of Defense Staff Gen. Bipin Rawat, his wife Madhulika Rawat, and 11 other military personnel, when it crashed in the southern state of Tamil Nadu last week. Singh -- the sole survivor -- suffered severe burns in the crash. The IAF said Singh succumbed to his injuries Wednesday morning. After his rescue from the wreckage, Singh was treated at the Military Hospital in the town of Wellington in Tamil Nadu, and was later transferred to the Command Hospital in the southern city of Bengaluru. Previously, the IAF said he had been in a "critical but stable" condition. "IAF is deeply saddened to inform the passing away of braveheart Group Captain Varun Singh," the IAF said in a statement on Twitter. "IAF offers sincere condolences and stands firmly with the bereaved family." Prime Minister Narendra Modi expressed his sadness over Singh"s death, and offered condolences to his family and friends. "Group Captain Varun Singh served the nation with pride, valour and utmost professionalism," Modi wrote on Twitter. "I am extremely anguished by his passing away. His rich service to the nation will never be forgotten." India"s Defense Minister Rajnath Singh -- no relation to Varun Singh -- said he was "pained beyond words" at the news. "He was a true fighter who fought till his last breath," Rajnath Singh wrote on Twitter. The IAF helicopter that crashed was a Soviet-designed Mi-17V-5. The cause of the crash is not yet known and the IAF has ordered an inquiry into the incident, which they said would be "completed expeditiously." Last week, India paid tribute to Rawat and the others who were killed. Rawat"s remains were cremated on Friday in the capital, New Delhi, with full military honors, according to the Indian Army. The last rites for all the other deceased military personnel were also given appropriate military honors. — CNN