NEW DELHI - India’s navy chief resigned on Wednesday after a submarine accident off the coast of Mumbai saw two sailors missing and another seven injured, the defence ministry said.

“Taking moral responsibility for the accidents and incidents which have taken place during the past few months, the Chief of Naval Staff Admiral DK Joshi today resigned,” a ministry statement said.

The seven sailors suffered breathing problems after trying to contain the smoke which filled the living quarters of the INS Sindhuratna during a training exercise, according to the navy.

Another two crew members have not yet been found on the Russian-built submarine, which was still seaworthy after the incident and was returning to port in Mumbai, the statement said.

They were airlifted from the submarine to hospital for treatment and navy ships were dispatched to help the vessel, said Narendra Kumar Vispute, a spokesman for the defence ministry. “The incident took place between 6am and 7am. The crew contained the smoke but seven of them had to be airlifted by naval helicopters. They are all stable,” Vispute told AFP, without giving the cause of the incident.

“Two personnel have not yet been located and all efforts are in progress to locate them,” the statement said. “All other crew of the submarine are on board and safe. Submarine is also safe and does not have any weapons on board.” Smoke filled compartment number three, triggering the emergency closure of hatches which isolate sections of the submarine, according to the Press Trust of India (PTI) news agency.

“Two officials are unaccounted for. They might have been left in the cabin or at some other place as various cabins and compartments are isolated as part of the emergency measures,” PTI quoted an unnamed navy officer as saying.

The incident comes after 18 naval crew were killed in August last year when the fully-armed Russian-built INS Sindhurakshak exploded in flames and sank in a military shipyard in Mumbai.

An inquiry was under way into the cause of Wednesday’s incident, which a navy spokesman blamed on sparks in the accommodation cabin. The submarine had only been handed back to the navy in December after undergoing a major refit, according to local reports. It had been undergoing exercises off the Mumbai coast as part of a clearance process for full operations when the incident occurred.

INS Sindhuratna is a kilo-class submarine which normally operates with a crew of 53 and can sail on its own for 45 days, the Indian navy website says. Last month another submarine, INS Sindhughosh ran aground while returning to Mumbai harbour. No loss of life or damage was reported.

In February 2010 the Sindhurakshak suffered a fire while docked in Visakhapatnam city in southern India, killing a 24-year-old sailor. The Indian navy has 14 submarines, but only between seven and nine are operational at any one time because of regular repair and refitting.

Russia is still the biggest military supplier to India, but relations have been strained by major delays and cost overruns with a refurbished aircraft carrier, the INS Vikramaditya. “The Indian navy has an ageing fleet of submarines and constant delays in acquiring new submarines,” said Sameer Patil, associate national security fellow at Mumbai think-tank Gateway House.