Satellite images appear to show several Russian warplanes at an airbase in Crimea have been damaged or destroyed.
Ukraine’s air force said on Wednesday that nine aircraft were demolished in explosions a day before – a claim Russia denied.
The images, from the US-based Planet Labs, show several warplanes in pieces and swathes of scorched earth.
One person was reportedly killed and more than a dozen others injured in the series of blasts at the Saky Russian military airbase, close to seaside resorts on the annexed Crimean Peninsula.
Kyiv has not publicly claimed responsibility for the attack, but a senior Ukrainian official told Sky News that Ukrainian Special Forces carried out the operation.
It would be the first known major attack on a Russian military site on the Crimean Peninsula, which was seized from Ukraine by the Kremlin in 2014 and used as a launchpad for the invasion of its neighbour in February.
Russian warplanes have used the base to strike areas in southern Ukraine.
Crimea holds huge strategic and symbolic significance for both sides.
The Kremlin’s demand that Ukraine recognise Crimea as part of Russia has been one of its key conditions for ending the fighting, while Ukraine has vowed to drive the Russians from the peninsula and all other occupied territories.
The Russian authorities sought to downplay the explosions, saying on Wednesday that all hotels and beaches were unaffected on the peninsula, which is a popular tourist destination for many Russians.
Moscow said the explosions were detonations of stored ammunition and had not been caused by an attack.
Russia’s main news agencies quoted an unnamed ministry source as saying that “only a violation of fire safety requirements is considered as the main reason for the explosion of several ammunition stores at the Saky airfield”.
Ukrainian officials appeared to mock Russia’s explanation that a careless smoker might have caused ammunition at the Saky airbase to catch fire and blow up.
In an apparently sarcastic post on Facebook, the Ukrainian defence ministry said: “The Ministry of Defence of Ukraine cannot establish the cause of the fire, but once again recalls the rules of fire safety and the prohibition of smoking in unspecified places.”
It added: “We can’t rule out that the occupiers will ‘accidentally’ find some characteristic ‘insignia’, ‘visiting card’ or even ‘DNA’.”
One tourist, Natalia Lipovaya, said that “the earth was gone from under my feet” after the powerful blasts.
Sergey Milochinsky, a local resident, recalled hearing a roar and seeing a mushroom cloud from his window. “Everything began to fall around, collapse,” he said.
A Ukrainian parliament member, Oleksandr Zavitnevich, said on Facebook the airfield – which houses fighter jets, tactical reconnaissance aircraft and military transport planes – was no longer usable.
Russia’s military industrial capacity is said to be “under significant strain”, and the credibility of many of its weapons systems undermined by their association with its forces’ “poor performance in the Ukraine war”, according to UK intelligence.
Russia has long considered the defence industry to be one of its most important export successes, the UK Ministry of Defence said.
But in its daily briefing on Thursday, the MoD said Russia was highly unlikely to be capable of fulfilling some export orders for armoured fighting vehicles because of the exceptional demand for vehicles for Russia’s own forces in Ukraine, and the increasing effect of Western sanctions.