A Russian military landing ship sails not far from Kerch, Crimea, on Monday, July 17, 2023. AP
The number of attacks in the sea has increased from both sides since Moscow exited a deal last month that had allowed Ukrainian grain exports via the shipping hub during the conflict between the two countries.
"Tonight, the Armed Forces of Ukraine, with the use of two unmanned sea boats, attempted an attack on the Novorossiysk naval base of the Russian Armed Forces," the defence ministry said on Telegram.
Russian ships destroyed the naval drones, it said. It was the first such attack targeting the port city.
The Black Sea port of Novorossiysk hosts the terminus of a pipeline that carries most Kazakh oil exports through Russia.
The fuel artery's operator Caspian Pipeline Consortium said it was continuing to ship oil to moored tankers at the terminal, Russian state media reported Friday.
But "a temporary ban has been established on the movement of ships in the port", said the company, as quoted by Interfax news agency.
Russia's Black Sea Fleet has been targeted since the beginning of Moscow's military campaign in Ukraine more than a year ago, but attacks have increased in recent weeks.
On Tuesday, Russia's defence ministry said it foiled a Ukrainian drone attack targeting patrol boats in the Black Sea.
Three drones were trained on ships navigating in waters 340 kilometres (210 miles) southwest of Sevastopol, the base of Russia's Black Sea fleet in Crimea.
A similar attack was repelled a week earlier.
- Crimea attack repelled -
The ministry also said Friday it had downed 13 drones over the Crimean peninsula.
There were no casualties or damage in either attack, the ministry said.
Crimea, annexed by Russia in 2014, has been targeted by Kyiv throughout Moscow's Ukraine offensive but has come under more intense, increased attacks in recent weeks.
Ukrainian drone attacks on Crimea in July blew up an ammunition depot and damaged a strategic and symbolic bridge linking Russia's mainland to the peninsula.
Kyiv has repeatedly said it plans to take back Crimea, which is a regular target for its forces.
On Sunday, Russian-installed authorities in Crimea said 25 Ukrainian drones were destroyed over the peninsula.
Kyiv says Russia has repeatedly attacked Ukraine's Odesa, a centuries-old city on the shores of the Black Sea and one of Ukraine's main ports.
- Frontline under microscope -
Also announced Friday was Russian Defence Minister Sergei Shoigu's visit to a combat zone in Ukraine to inspect a command post and meet senior military officers.
Shoigu got an update on the situation on the front and "thanked commanders and soldiers... for successful offensive operations" in Lyman in eastern Ukraine, the army said, without mentioning when the visit took place.
Shoigu last visited the front at the end of June after a failed rebellion by the Russian paramilitary group Wagner fighting along with Moscow's forces in Ukraine.
Ukraine began its long-awaited counteroffensive in June but has made modest advances in the face of stiff resistance from Russian forces on the frontline.
Ukrainian President Volodymyr Zelensky said Thursday that the counteroffensive was difficult, reporting "very violent" fighting in the key areas on the eastern and southern fronts.
Late summer and early autumn 2022, Ukraine retook swathes of territory around Kherson and Kharkiv in rapid counteroffensives.
But Ukrainian forces are now contending with well-entrenched Russian defensive positions built over several months.