On Tuesday, there were reports of a series of explosions at a Russian military air base in Crimea.
One person died and five were injured in the explosions, according to the Ministry of Health of the Crimean Peninsula.
Russia claims no warplanes were damaged in the explosions - but satellite images appear to show at least eight damaged or destroyed warplanes, the BBC reports.
If the number of destroyed planes is correct, it could mean the country's largest single-day loss of combat aircraft since World War II, according to CNN.
Great Britain: It was Ukraine
The fact that two explosions are reported to have occurred, according to British Defense Minister Ben Wallace, indicates that it is a Ukrainian attack, contrary to what both countries claim.
According to Russia, the explosions were caused by an accident in an ammunition depot.
Ukraine also denies carrying out an attack, suggesting an accident must have occurred.