Russia's defence ministry said early on Friday that it had thwarted overnight Ukrainian attacks on a naval base in the Black Sea and the Crimean peninsula.
"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 ministry said on Telegram.
Russian ships destroyed the naval drones, it said.
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, where tensions have been building after Moscow exited a deal protecting Ukrainian grain exports.
A similar attack was repelled a week earlier.
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, meanwhile, has repeatedly attacked Ukraine's Odesa region, on the shores of the Black Sea.
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