The Russian Baltic Fleet minesweeper Alexander Obukhov was put out of action thanks to a sabotage operation by Ukraine's military intelligence, the agency said on Oct. 7.
The ship, based in the Russian coastal town of Baltiysk in the Kaliningrad exclave, reportedly "suffered severe damage" after water leaked into the engine due to "the mysterious appearance of a hole in a gas duct."
This is the second case of Ukraine sabotaging a Russian warship in the exclave, which lies between Poland and Lithuania some 400 kilometers (250 miles) from Ukraine's northwestern border.
The vessel that was supposed to be sent on duty is now undergoing major repairs, as the damaged M-503 engine is a rare piece of equipment, the agency noted. Efforts to fix the vessel are likely to be "technically difficult and expensive," according to HUR.
The agency published a video supposedly from inside the Russian vessel, where an unidentified person shows and describes the aftermath of the sabotage, putting the date as Sept. 30.
HUR did not specify how it gained access to the vessel to carry out the sabotage.
In another incident on April 8, the Russian missile ship Serpukhov was set on fire while docked off the Kaliningrad exclave.
Ukraine later revealed that a then-active member of the Russian Armed Forces assisted with the sabotage operation.
Kyiv's forces also managed to disable roughly one-third of the Russian Black Sea Fleet with drone and missile attacks, undermining Russia's naval dominance in the sea.