A Russian boat has been destroyed in the Black Sea in a devastating blow for Vladimir Putin's military.
Dramatic footage posted on social media by Defence Intelligence of Ukraine showed the Russian missile boat in a special operation off Russian-occupied Crimea.
According to the Ukrainians, the Ivanovets, a small warship, received "direct hits to the hull" overnight, after which it sank. Black and white video appears to show a massive explosion taking place before the ship tilts almost 90 degrees and sinks.
However, Russian military experts speculated the boat had been targeted by naval drones.
Footage posted by Defence Intelligence of Ukraine showed the explosion
Defence Intelligence of Ukraine
Ukraine's Main Intelligence Directorate said the boat was destroyed by soldiers of its special unit "Group 13" in Lake Donuzlav, a saltwater bay on the western side of the Crimean peninsula which houses a naval base.
On social media, it wrote: ""As a result of a series of direct hits to the hull, the Russian ship suffered damage incompatible with further movement, the Ivanovets listed to the stern and sank."
However, Russian military blogger "Voenkor Kotenok" wrote on Telegram that the boat had sunk after being hit three times by naval drones.
Foreign Ministry official Olexander Scherba described the attack as "impressive", telling the BBC: "At 03:45 [01:45 GMT] there was the first hit and at 04:00 the whole crew was evacuated already. So there was no chance at all that this vessel would be saved."
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The explosion on the vessel
Defence Intelligence of Ukraine
Earlier this week, the Russian Defence Ministry said in a statement on Wednesday it had completed an exchange deal with Ukraine under which each side got 195 soldiers back.
It said its own soldiers would be flown to Moscow to receive medical and psychological treatment. It was the first such exchange since the crash of a Russian military transport plane last week that Moscow says was carrying 65 Ukrainian soldiers ahead of a planned exchange.
Russia says Ukraine shot down the plane with a ground-to-air missile and that all 74 people on board were killed.
Ukraine has neither confirmed nor denied that it downed the plane, and has demanded proof of who was on board.
Meanwhile, the head of Ukrainian military intelligence said on Tuesday he expected Russia's offensive on the eastern front line to fizzle out by early spring.
Head of Ukraine's military intelligence agency GUR Kyrylo Budanov said on national TV: "(Russia's) offensive is still ongoing. Somewhere in early spring, it will be exhausted completely.
Budanov played down the Russian forces' gains, saying they had only achieved "a few advances across some fields" and near the embattled town of Avdiivka.
He added: "Now it's the enemy's move. It will end, and I think ours will start."