A big Russian amphibious ship, the Caesar Kunikov, has been sunk off the coast of Russian-occupied Crimea, according to Ukraine's armed forces.

Powerful explosions were heard early on Wednesday, according to local social media, which suggested the landing ship was hit south of the town of Yalta.

Ukraine's intelligence directorate released video of what it said were Magura V5 sea drones striking the ship.

Ukraine has repeatedly hit Russia's Black Sea fleet in occupied Crimea.

Satellite images last year showed much of the fleet had left the peninsula for the Russian Black Sea port of Novorossiysk.

Ahead of a Nato ministerial meeting in Brussels, the secretary general of the Western defensive alliance, Jens Stoltenberg, said Ukrainian forces had won a "great victory" in recent months, inflicting "heavy losses" on the Black Sea fleet that had opened a corridor for Ukrainian grain exports.