"Today at 22.55 (1955 GMT), the armed forces of Ukraine made an unsuccessful attempt to attack the ships of the Black Sea Fleet with an unmanned sea boat," the ministry said in a statement.

"The ships were performing the tasks of controlling navigation in the southwestern part of the Black Sea, 237 km (147 miles) southwest of Sevastopol."

Sevastopol is the base of Russia's Black Sea Fleet on the Moscow-annexed Crimean peninsula.

The ministry said the drone was destroyed by the Pytlivyi and Vasily Bykov patrol ships before it could reach its target.

Attacks from both sides have escalated in the Black Sea since Russia pulled out of a deal that had allowed safe export of Ukrainian grain through the shipping hub.

On August 4, Russia said it had repelled Ukraine's attempted drone attack on its Novorossiysknaval base in the sea, while a Ukrainian security source said the strike on a warship at the base was successful.

A day later, a Ukrainian drone hit a Russian oil tanker south of the Kerch Strait.

Thursday's attack comes hours after a civilian cargo ship sailing through the Black Sea from Ukraine reached Istanbul in defiance of a Russian blockade.

Moscow announced last month that it would consider any ships nearing Ukraine in the Black Sea as potential military cargo carriers.

Days ago, the Vasily Bykov patrol ship fired warning shots and boarded a Turkish-owned but Palau-flagged cargo vessel that was sailing to a Ukrainian river port.

Russia has also ramped up attacks on Ukraine's port infrastructure in the Black Sea and the Danube River, a vital export route since the grain deal's scrapping, in recent weeks.