KYIV, Ukraine — Ukrainian sea drones attacked a major Russian port Friday, damaging a naval ship, according to a Ukrainian official, as the Black Sea becomes an increasingly important battleground in the war. Moscow claimed it repelled the attack.

The strike on Novorossiysk — which halted maritime traffic for a few hours — marks the first time a commercial Russian port has been targeted in the 18-month conflict. The port — which hosts a naval base, shipbuilding yards and an oil terminal and is key for exports — lies just across the Black Sea from Crimea, where Russia’s Defense Ministry said it thwarted another attack overnight.

The Security Service of Ukraine and the country’s navy carried out the attack on Novorossiysk, according to an official with the security service, and the landing ship, Olenegorsky Gornyak, suffered a serious breach. As a result, the ship is unable to carry out its combat missions, the official added, speaking on condition of anonymity because he was not authorized to give the information to the media. Images posted on social media showed a ship listing.

Friday’s attack is the latest in the latest in a series of strikes inside Russia. It also reflects an increase in fighting in the Black Sea following Moscow’s withdrawal from a deal that allowed Ukraine to export its grain through the waterway. On Wednesday, Russian drones caused significant damage and a huge fire at grain facilities in the Odesa region. A day earlier, the Russian military said Kyiv’s forces tried to attack two patrol vessels in the sea, southwest of the Russian-controlled city of Sevastopol in Moscow-annexed Crimea.

Mykhailo Podolyak, an advisor to Ukrainian President Volodymyr Zelenskyy, heralded the latest attack, saying it showed “drones are changing the rules of the game … and ultimately destroying the value of the Russian fleet.”

Russia has Far Superior Navy

Russia’s far superior navy has controlled the seas in the war so far. Its ships fire on major ports and cities across Ukraine, and they have largely blockaded the country’s coast as well as mining the Black Sea, making passage through it treacherous. Podolyak’s remarks and other recent attacks in the sea and on the Kerch Bridge connecting Crimea to Russia could indicate Ukraine is trying to change that dynamic.

With the latest assault, “Kyiv showed that it can attack any vessel of the Black Sea Fleet, no matter the distance,” said Ukrainian military analyst Roman Svytan.

The end of the grain deal, under which ships carrying food from Ukrainian ports were promised safe passage, “untied Kyiv’s hands,” he said, predicting the frequency of attacks on Russian ships would only increase.

Taking on Russia on the seas, however, will be a serious challenge. Russia’s navy dwarfs Ukraine’s — and after Moscow annexed Crimea in 2014, Ukraine said it lost more than 80% of its naval capabilities. Meanwhile, Russia’s Black Sea Fleet has 279 vessels, including 52 warships. So far, Ukrainian attacks have destroyed at least two: the Saratov landing ship, which sank in the occupied port city of Berdyansk early on in the war, and the fleet’s flagship, the Moskva, which also sank early in the war. Several more have been reportedly damaged.

On Friday, Ukrainian news agencies carried footage from social media channels that showed a ship listing to one side that they suggested was the Olenegorsky Gornyak. The ship is designed to transport troops and heavy equipment and was sent for repairs in 2014, according to Russian media reports. It is normally based with Russia’s Northern Fleet in the Arctic.

Russia claimed it fended off the attack, saying ships patrolling the perimeter of the naval base, including the Olenegorsky Gornyak, destroyed two sea drones. The Caspian Pipeline Consortium, which operates an oil terminal in the port, said maritime traffic was halted for a few hours but that its facilities were not damaged. The regional governor said there were no casualties.

Footage published on Russian social media channels appeared to show a ship firing into the sea and a burning object exploding. Ukrainian social media channels also posted nighttime video shot from what they indicated was a sea drone, floating near a ship.

The Associated Press could not verify the videos.

Kremlin spokesman Dmitry Peskov refused to comment on the attack during a conference call with reporters.

Minutes after confirming the attack on the Black Sea port early Friday morning, Russia’s Ministry of Defense said it had also repelled another attack by Ukraine on Crimea. The ministry said air defense systems shot down 10 drones and it had electronically jammed another three.

Videos shared on Russian social media channels reportedly from around the city of Feodosia showed what appeared to be air defense systems working, as well as loud explosions. Feodosia is just across the water from Novorossiysk and is not far from Kerch, which was attacked in July. Russian officials blamed the attack on the Kerch bridge — which left a span of the roadway hanging perilously — on Ukraine. The bridge is a key artery for military and civilian supplies from Russia to Crimea and is an assertion of Kremlin control of the peninsula it illegally annexed.