It said in a tweet that the helicopter “met with a tragic accident” and one air force officer, Group Captain Varun Singh, survived and was being treated in a military hospital.
Public broadcaster Prasar Bharati said the Mi-17V5 helicopter was on its way from an air force base to the army defence services college when it crashed near the town of Coonoor, a hill station in Tamil Nadu. The reason for the crash was not immediately known.
SP Amrith, a senior civil administrator of the area where the crash took place on Wednesday, said rescuers were able to save one male passenger, who was taken to a hospital for treatment.
Mr Amrith said the helicopter had a total of 14 people on board.
Defence Minister Rajnath Singh was expected to make a statement to Parliament.
Television images from the crash site showed plumes of smoke billowing from the debris as local residents tried to put out the fire and remove bodies from the wreckage.
The air force said in a tweet that an inquiry has been ordered into the accident.
Mr Rawat, 63, was the most senior official in the Indian military and the first chief of defence staff, a position created by the government in 2019.
He wass also an adviser to the Defence Ministry and handles coordination and integration of the combat capabilities of the armed forces.
Mr Rawat previously served as chief of army staff.