Ukrainian drones struck eight tankers from Russia's so-called "shadow fleet" that were delivering fuel to Crimea overnight, Kyiv's military said on Tuesday, part of a mounting effort to isolate the annexed peninsula.

In a statement on Telegram, Ukraine's drone forces said they struck the vessels — each under international sanctions and with a deadweight of around 7,000 tons — in the Sea of Azov.

"Striking the enemy's naval logistics complicates the supply of fuel and ammunition necessary to support the activities of Russian troops, primarily in the temporarily occupied territory of Crimea," Ukraine's drone forces said.

The unit posted black-and-white, drone-view footage showing ships being targeted and erupting into flames. Reuters could not independently verify the information.

It came a day after Ukraine said it hit two other "shadow fleet" vessels around the same area.