At least 14 crew members were killed in Russia after a fire breakout aboard aboard a Russian navy research submersible, the Russian defence ministry says.
Details remained sketchy but reports suggested that the crew was poisoned by fumes as the vessel was taking measurements in Russian territorial waters on Monday.
Russian media reports say it was a nuclear mini-submarine used for special operations.
The fire was later put out and the vessel is now at Severomorsk, the main base of the Russian Northern
Though the defence ministry did not say how many crew members were aboard at the time. Reports in local media say several crew were injured and taken to hospital.
An investigation into the incident has begun under the commander-in-chief of the navy.
Russian President Vladimir Putin later on Tuesday pulled out of a scheduled event in the Tver region, north-west of Moscow, to discuss the issue with Defence Minister Sergei Shoigu.
It was not clear what caused the fire which the crew ultimately brought under control and it is not known how many survived.
President Putin said the dead included two heroes of Russia and seven captains “of the first rank”- which seems unusually senior – for research work.
Some media in Russia are citing sources saying they could have been on board a nuclear-powered submarine, possibly even the secretive AS-12. It is thought to be used for highly sensitive missions.