Direct proof of use
The documented conflict use of the Kara-class cruiser was not as an operational combatant, but as a blockship. On the night of March 5-6, 2014, Russian forces towed the decommissioned Ochakov, a Project 1134B / Kara-class anti-submarine cruiser, into the navigable channel at the entrance to Lake Donuzlav and sank it to block Ukrainian Navy ships based at Novoozerne.
Ukrainian Ministry of Defence reporting, carried by Interfax-Ukraine and Naval Today, said Russian forces filled Ochakov with water, an explosion followed, and the ship came to rest in 9-11 meters of water, preventing vessels from leaving Donuzlav. UNIAN separately reported the same sequence from a military source in Sevastopol.
Sources: Interfax-Ukraine Donuzlav Report, Naval Today Ochakov Report, UNIAN Donuzlav Source Report
Donuzlav blockade
The scuttling took place during Russia's seizure of Crimea, when Russian Black Sea Fleet ships were already blocking the exit from Donuzlav. Reports identified the cruiser Moskva among the vessels that had been positioned near the channel before Ochakov was placed between the northern and southern spits at the lake entrance.
The immediate military effect was area denial rather than firepower. Ochakov's hull physically obstructed the channel and helped confine Ukrainian naval vessels inside Donuzlav, separating possession of a retired Russian hull from its use as a maritime obstacle in the conflict.
Sources: MarineLink Obstacle Report, UNIAN Donuzlav Source Report, gCaptain Ochakov Report
Aftermath and identification
GlobalSecurity's Project 1134B class listing identifies Ochakov as the second Kara-class ship and notes that it was sunk as a blockship in March 2014. A Ukrainian Ministry of Defence image later archived on Wikimedia Commons shows the sunken Ochakov in Donuzlav on March 6, 2014, providing visual context for the blockship use.
The evidence does not show Project 1134B weapons, sensors, or propulsion being used in combat during the war. The conflict-specific role was the deliberate scuttling of the decommissioned hull to obstruct Ukrainian naval movement during the Crimea operation.
Sources: GlobalSecurity Project 1134B Ship List, Wikimedia Commons Ochakov Image