MOSCOW, January 30. /TASS/. The Black Sea Fleet submarine Stary Oskol arrived at the Kronstadt Marine Plant for planned repairs after its deployment in the Russian Navy’s permanent Mediterranean taskforce, a source in Crimean defense circles told TASS on Wednesday.

"Last night, an operation was fulfilled to place the submarine into the dock of the Kronstadt Marine Plant," the source said, adding that the sub’s planned repairs would last up to four months.

The same-type submarine Krasnodar continues its deployment to the Mediterranean Sea within the Russian Navy’s permanent Squadron in that area. Initially, these two subs were expected to undergo repairs at the Admiralty Shipyard in St. Petersburg, which had built them. However, later, this task was assigned to the Kronstadt Marine Plant (both shipyards are part of Russia’s United Shipbuilding Corporation).

In late April 2019, the Krasnodar and the Stary Oskol deployed to the Mediterranean Sea from the Black Sea, replacing the same-type submarines Veliky Novgorod and Kolpino in the Russian Navy’s permanent Mediterranean taskforce.

Project 636.3 submarines are referred to the third generation of diesel-electric subs. These submarines are considered among the world’s most noiseless vessels. They develop a speed of up to 20 knots, can dive to a depth of about 300 meters and their sea endurance is 45 days. The sub has a crew of 52 men and displaces about 4,000 tonnes.