It said in a tweet that the helicopter "met with a tragic accident".

The dead included Rawat's wife.

The air force said one officer, Group Captain Varun Singh, survived and is 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.

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 an inquiry has been ordered into the accident.

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 was also an adviser to the Defence Ministry and handles co-ordination and integration of the combat capabilities of the armed forces.

Rawat previously served as chief of army staff.

Australian Associated Press