MUMBAI: Seven Indian sailors were injured in an accident on a submarine off Mumbai on Wednesday, the navy said, with reports of another two missing in the latest incident to hit the force.

The seven sailors suffered smoke inhalation and were airlifted from the submarine for treatment, navy spokesman Rahul Sinha said, without disclosing details of the incident.

“The submarine was on a routine training sortie off Mumbai's coast when smoke was detected. Measures were taken to contain it,” Commander Sinha told the NDTV news channel.

“All the sailors are currently undergoing treatment under the supervision of a team of doctors. But I do not have details.”

Naval ships have already taken up posts around the Russian-built INS Sindhuratna to provide help, Sinha added.

Another two crew members were missing, according to the Press Trust of India news agency which cited unnamed navy officials.

The seven injured sailors fell unconscious after a leak in the submarine's battery compartment during the training exercise near Mumbai harbour, PTI said, citing navy sources.

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

The disaster was thought to be the Indian Navy's worst since the sinking of a frigate by a Pakistani submarine in 1971.

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.