Russia is set to deploy one of the quietest attack submarines in the world, nicknamed "black hole," to the Pacific Ocean sometime this fall.

Newsweek reported, citing Russian state-owned media outlet Izvestia, the diesel-electric submarine, which was commissioned in November, will move from the Baltic Sea to the Pacific at an unspecified date in the fall.

The Ufa, one of Russia's Project 636.3 diesel-electric submarines, is touted as an advanced stealth vessel. The U.S. Navy and NATO have referred to the submarine as a "black hole" because it is said to be among the world's quietest submarines.

Russia's Pacific Fleet forces started operational exercises Monday in the Sea of Japan and the Sea of Okhotsk that will last until June 20, Reuters reported, citing Russia's Defense Ministry.

According to TASS, the subs are about 240 feet long and displace more than 3,900 tons. Because of their strong hulls, the submarines have an operational depth of 787 feet and can dive to a maximum depth of 984 feet. The submarines have an operational range of up to 7,500 miles. They are armed with Kalibr-PL cruise missiles that are launched from torpedo tubes.

The U.S. Navy has 71 submarines, all nuclear-powered. Russia's submarine fleet of 58 has a large percentage of diesel-electric-powered subs, with 21 compared with 37 that are nuclear-powered, according to the nonprofit Nuclear Threat Initiative.

In a March analysis, the NTI said Russia signed a contract for six Project 636.3 submarines in 2016, with the first submarine launched in March 2019.

In November, Admiralty Shipyards, which produces the Project 636.3 submarines, said the fourth vessel, the Ufa, was accepted into the Pacific Fleet. The fifth submarine in this series, the Mozhaisk, was launched in late April. The sixth and final vessel, the Yakutsk, is scheduled to be handed over to Russia's Navy in 2024.

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