While the frontline on land has remained static for over a year, Ukraine claims to have put Russia on the defensive in the Black Sea, an area vital for Ukrainian exports.

Its military said its forces together with military intelligence units had "destroyed" the "Caesar Kunikov" Russian landing ship off the coast of the Crimean peninsula.

A large ball of smoke and flames could be seen rising from what appeared to be a ship in footage posted by Ukrainian military intelligence.

"The enemy ship was attacked by Magura V5 maritime strike drones off the coast of the temporarily occupied Crimea near the city of Alupka," it said.

Moscow said it had downed six Ukrainian drones over the strategic body of water.

Crimea, annexed by Moscow in 2014, has been extensively targeted by Ukrainian drones and missiles since it began its counteroffensive last summer.

Ukraine says its attacks have put a third of Russia's Black Sea warships out of action since the invasion began, as it seeks to protect its shipping routes and prevent attacks from the sea.