Quote 'Involved in top secret missions on the Arctic seabed
In 2012, the vessel was involved in research intended to prove Russia's claim on the vast Arctic seabed.
It collected samples from the depth of 2,500 metres, according to official statements at the time. Regular submarines can typically dive to depths of up to 600 metres.
Some observers have speculated that the vessel could be capable of going as deep as 6,000 metres.
Analysts have suggested one of its missions could be disrupting communication cables on the ocean bed.
The Losharik is carried under the hull of a mother submarine, the nuclear-powered Orenburg.
Russian news reports said that while the Losharik officially belonged to the Northern Fleet, it answered directly to the Defence Ministry's Department for Deep-Sea Research, reflecting the high sensitivity of its missions.
The Russian navy also uses Priz-class and Bester-class deep water vehicles, which have a hulls built of titanium and are capable of operating at a depth of 1,000 metres.
The small vehicles have a crew of two and are primarily intended for rescuing submariners in case of incidents.
Such vessels are transported to the area of operation by a carrier vessel and can operate autonomously for up to 120 hours.'