A suspected Ukrainian suicide drone has washed up on a beach near a Russian naval base.
The weapon was discovered in Omega Bay near the Crimean port of Sevastopol, which was previously annexed by Russia.
It is believed the remote-controlled vehicle, which is still intact, was donated to Ukraine by the US.
Writing in Naval News, submarine expert H. I Sutton said: "A theory is that this device is designed to ram another vessel and detonate, like a modern interpretation of an explosive boat.
“This also explains the cluster of sensors at the bow.”
He added that the boat appeared to have evaded Russian patrol vessels.
The kayak-sized drone is said to be supported by just a single motor, powering a waterjet.
Russian forces said they destroyed the boat after discovering it on the beach.
The weapon may have been helping Ukrainian special forces, who are operating amphibious attacks in the south of their country.
It comes just a month after footage showed the aftermath of 15 explosions at a Russian airfield in Crimea.
The explosions happened near the town of Saki, the home to Russia's 43rd Air Regiment.
Footage showed wrecked cars from a series of explosions at the military base as frightened Russian tourists were seen hurrying from beaches amid the chaos.
Huge plumes of smoke and mushroom clouds were seen in the aftermath.
Ukraine neither confirmed nor denied an air missile attack on the airfield while also hinting at sabotage by partisans on the peninsula, and warning: “This is just the beginning.”
One person was killed and nine wounded in the blasts, said the Russian authorities in Crimea.
The footage appeared to show massive damage consistent with a major attack even if the cause remains unclear.
As well as the destroyed warplane, a car is seen skewered by a long metal object, apparently due to a blast.
Russia claimed the explosions were caused by ammunition explosions but this was decried even by pro-Moscow sources.
A similar explanation of exploding munitions was given by Russian defence officials when the Moskva cruiser was in fact sunk by Ukrainian missiles in April.
Some Ukraine sources hinted at a missile strike, even though no incoming rockets were seen on footage of the incident.
"As you can see, missiles with a range of 200-300km are already being used in our country," said Viktor Andrusiv, previously an adviser to Ukraine's Interior Ministry.
“The explosions in Melitopol and…at Novofedorivka…are proof of this.”
