A Ukrainian naval drone hit a Russian oil tanker early on Saturday off the occupied Crimean Peninsula, Russian officials said, the second attack on the country’s ships in the Black Sea in two days.

Ukraine’s maritime authority also posted a bold warning online on Saturday saying that all Russian Black Sea ports and approaches to them would be considered a “war risk area starting August 23”.

The attacks and the warning come as tensions mount in the Black Sea, where Russia has attempted in recent weeks to cut off Ukraine’s access to the sea’s vital shipping routes.

The engine room of the tanker was damaged, but the ship remained afloat, there was no oil spillage and no crew members were injured, Russia’s Federal Agency for Sea and Inland Water Transport said on the social messaging service Telegram. Vasyl Malyuk, the head of the Security Service of Ukraine, said the country was responsible for recent attacks on Russian vessels, calling them a “logical” and “effective” tactic — without explicitly mentioning Saturday’s strike.

The tanker was near the Kerch Strait Bridge, a vital connection for Russia to the Crimean Peninsula, which has been under Russian occupation since 2014. Malyuk suggested that Ukraine would continue attacking the bridge until Russian forces completely withdrew from Ukrainian lands.

Russia accused Ukraine of attacking the bridge itself last month, also with sea drones.

The attack on Saturday was an apparent continuation of Ukraine’s challenge to Moscow’s control of the Black Sea. A day earlier, the country’s forces had demonstrated the expanding reach of their uncrewed vessels by hitting a Russian ship near the Russian port of Novorossiysk, 644km by sea from the nearest Ukrainian-held shores.

The Russian agency said the vessel damaged on Saturday was the oil and chemical tanker Sig, and that it had been approaching the Kerch Strait Bridge from the south with a crew of 11. Rybar, a popular Russian pro-war blog, said the tanker was returning from delivering oil to Syria.

In the attack, the previous day near Novorossiysk, a Russian shipping and naval hub on the northeastern shore of the Black Sea, a naval drone appeared to slam into a Ropucha-class landing ship that was later seen listing to its port side in photos and videos verified by The New York Times.

New York Times News Service