File pic: Admiral DK Joshi, Chief of Naval Staff, Indian Navy

Navy Chief Admiral DK Joshi has resigned after a submarine accident off the Mumbai coast this morning. An official statement said he had stepped down taking moral responsibility for the "accidents and incidents which have taken place during the past few months." (Read Defence Ministry's statement) Admiral Joshi is the first military chief to resign. He took charge in 2012, had more than a year left in service. The Defence Ministry immediately accepted his resignation. Vice Admiral RK Dhowan will officiate till a new chief is appointed. ( Also see: Admiral DK Joshi's interview to NDTV in November 2013 This morning, a fire reportedly broke out in the crew accommodation area of the 25-year-old Indian Navy submarine INS Sindhuratna, which was being sea tested after a refit, about 50 kilometres off the Mumbai coast. Seven sailors fell unconscious from suffocation while trying to control the fire and smoke and had to be airlifted to a Navy hospital in Mumbai. Two officers are reported missing. ( Seven sailors injured, two officers missing after accident on INS Sindhuratna The senior-most submarine officer of the Western Naval Command was on board.The submarine surfaced after the smoke was detected. The fire fighting system activated immediately and compartments were sealed automatically. Helicopters were launched for rescue.The vessel is now on its way to Mumbai. At current speed of about three to four knots an hour, it is expected to take about 12 hours to reach.The Russian-origin Kilo Class submarine, one of India's 14 conventional submarines, was carrying no weapons or ammunition. It had sailed out last night and since it was still being tested, had not been placed under operational command yet.Defence Minister AK Antony briefed President Pranab Mukherjee, who is also the Supreme Commander of the Armed Forces, and Prime Minister Manmohan Singh on the accident.This is the 10th mishap involving an Indian Navy asset and the third submarine accident in the last seven months.In August last year, Navy submarine INS Sindhurakshak sank in the Mumbai harbour after an explosion on board, killing 18 sailors. ( Navy hopeful of reusing INS Sindhurakshak

Earlier this month, an amphibious warfare vessel INS Airavat ran aground after which its commanding officer was stripped of his command duties.