Russia said on Thursday that it had repelled attacks on one of its naval ships and other targets in Crimea, while Ukraine claimed it had struck a Russian air defence system in its latest assaults on the Russian-occupied region.

The attacks on Thursday came one day after Ukraine’s military struck two ships that were being repaired at the headquarters of the Black Sea Fleet, in one of the boldest assaults by Ukraine on Russia’s military infrastructure in Crimea, which Russia invaded in 2014 and illegally annexed.

The Russian navy destroyed five Ukrainian maritime drones at about 5am local time that were headed towards the Sergey Kotov, a patrol ship stationed in the Black Sea, the ministry of defence said in a statement on Telegram. Russia had used the Sergey Kotov to patrol the Black Sea after it backed out of a deal earlier this year that had allowed Ukraine to use the waterway to ship grain.

The ministry said later Thursday that its air defences had destroyed another 11 drones over the Crimean Peninsula and did not mention any damage. The Russian claims could not be immediately verified.

Ukraine’s military said it had struck Russian air defence systems near the town of Yevpatoriya in western Crimea in a long-range overnight attack on Thursday. Video on social media, which could not be verified, showed explosions in a few areas in Crimea, including Yevpatoriya, northwest of the port city of Sevastopol.

As Ukraine presses a grinding counteroffensive in the east and south of the country, it has also been conducting strikes far from the front lines in an apparent attempt to disrupt Russian logistics that feed Moscow’s war effort. It remains unclear, however, if the strikes have affected Russia’s broader operations on the battlefield.

Since 2014, Russia has built bases and supply routes in Crimea. Russia used those facilities to launch the full-scale invasion of Ukraine last year and as a base from which to fire missiles and drones at targets across Ukraine.