Multiple explosions shook a Russian military base in Crimea on Tuesday, the latest in a spate of similar incidents on the occupied peninsula.
The blasts happened at an arms dump in the town of Mayskoye in northern Crimea.
Russia's defence ministry said "sabotage" was to blame for the series of explosions, having previously claimed they were triggered by a fire which detonated ammunition.
It has not reported any serious casualties, but a local Russian-appointed official said two people were left injured.
The exact cause of the explosions is unclear, though there are unconfirmed suspicions it was an act of Ukrainian sabotage.
Videos posted online show a huge fireball at the temporary military facility near the city of Dzhankoi, which broke out at around 6:15 am local time.
A fire at an electricity substation was also reported 20km away.
Last week several Russian warplanes were destroyed in an apparent Ukrainian attack on a Russian military base in Crimea, which Moscow called an accident.
Ukraine has neither confirmed nor denied playing a role in either of these incidents.
Moscow called this an accident, though simultaneous blasts across the base left craters that are visible from space.
The UK Ministry of Defence said the incident had "significantly degraded" the capability of Russia's armed forces in the Black Sea.
Ukrainian presidential office adviser Mykhailo Podolyak described today's events as "demilitarisation in action", hinting they were not accidental.
The Crimean peninsula, which Russia annexed from Ukraine in 2014, is the base for Russia's Black Sea Fleet and a popular holiday resort in the summer.
"Occupied Crimea became a military base, filled with rockets and weapons," tweeted Anton Gerashchenko, advisor to Ukraine's Ministry of Internal Affairs on Tuesday morning.
"Tourists are fleeing. Hospitals are overflowing with wounded. [There is] environmental catastrophe. Is this the Crimea that Crimeans wish for," he added.
Kyiv aims to disrupt Russian supply lines ahead of a planned Ukrainian counter-attack, according to Reuters.
Mayskoye is on the main railway line linking Crimea with Russia, which Moscow uses to supply its army in southern Ukraine.
The arms depot is beyond the range of weapons supplied to Ukraine by the West, suggesting that the explosions could be some form of attack or that Kyiv has acquired the ability to strike deeper into Russian territory.