The crew of a Russian Varshavyanka-class diesel submarine takes part in a Victory Day parade in Vladivostok, Russia, May 9, 2015. Reuters/Host Photo Agency/RIA Novosti

Russia recently launched the world's longest nuclear-powered submarine that is also capable of carrying out underwater espionage missions, according to reports. The submarine, named Belgorod, is equipped to launch Poseidon nuclear torpedoes and can dive to around 1,700 feet.

The massive submarine was launched at Russia's Sevmash shipyards on April 23rd while President Vladimir Putin watched via satellite, state news agency TASS reported. Belgorod, also officially known as Project 09852, is a special purpose sub that is meant to act as a 'mothership' to Russia's other underwater vessels. Apart from its ability to launch the nuclear Poseidon drones, it is also reportedly designed to carry a Losharik class mini sub that can be attached to the bottom of Belgorod's hull.

The 230-ft-long Losharik mini subs are nuclear powered and boast of robotic arms. The mini subs are also capable of diving to depths of over 3,000 feet. Presumably, a Losharik sub attached to the Belgorod may come in handy during underwater spying missions.

“Belgorod was originally laid down as an Oscar-II class cruise missile submarine, but work stopped when the Russian economy caught up with the submarine building program. Work restarted years later in her modified form. So she is already older than many of her crew," H I Sutton, an expert on underwater warfare, told Popular Mechanics. “The modifications are likely to be extensive, and may include some latest technology, but underneath she is still an earlier generation of submarine, and likely to be less stealthy than the latest generation.”

According to Sutton, the details about Belgorod's capabilities remain unclear. Historically, Russia has been more successful in keeping its military capabilities a secret from the rest of the world.

“Russia has generally been more successful than the US at protecting her latest submarines from unwanted cameras,” Sutton said. “Just this week documents allegedly leaked of a nuclear triad briefing for President Trump included a cutaway of the as-yet unbuilt Colombia class ballistic missile submarine. For Russia's latest boats we are still guessing many details."

Belgorod's primary role is likely meant to be its covert placement of the Harmony submarine detection network, Sutton believes. Harmony is reportedly an underwater nuclear-powered detection system that is capable of sounding the alarm to the Russian military about any adversarial subs travelling through key areas.

Tests for Belgorod's nuclear reactor are scheduled for later this year, while its sea and state trials will reportedly take place in 2020.