A Russian Oscar II-class nuclear-powered submarine has caught fire while in dry dock. The boat is located in the Zvyozdochka shipyard in the northern province of Arkhangelsk.
It's understood there are no initial casualties with the TASS news agency quoting a source as saying the vessel's nuclear reactor had already been shut down and weapons removed.
It's believed that the fire started as a result of wielding work and that the insulation between the submarine's hulls is burning.
A spokesman for the shipyard had told the RIA Novosti news agency that the fire started close to the stern of the sub and that fire crews were tackling the blaze.
It's now understood that preparations are being made to flood the dock with water after efforts with foam failed to extinguish the fire.
The K-266 Oryol attack boat is from Russia's Northern Fleet - entering service in 1992 and currently undergoing an overhaul which should extend its life until at least 2016.
Fires are among the biggest threats to submarines with their crews extensively drilled in handling such incidents.
On this day in 1989 a developmental Russian nuclear submarine, the K-278 Komsomolets, sank after a fire broke out during its first operational patrol.
K-278 now rests a mile deep in the Barents Sea, its nuclear reactor and two nuclear warheads still on board.
The Kursk, which sank in 2000 with all 118 hands, was also an Oscar-II class nuclear submarine. It was lost when one of its torpedoes failed during a practice launch - causing a massive explosion which sent the vessel to the bottom. (ends)