Russia's defence ministry said on Tuesday a fire that set off explosions at a munitions depot in Moscow-annexed Crimea were caused by an act of "sabotage".

"On the morning of August 16, as a result of an act of sabotage, a military storage facility near the village of Dzhankoi was damaged," the ministry said in a statement carried by Russian news agencies. It added there were "no serious injuries".

Images posted on social media showed huge fireballs erupting at the site and clouds of black smoke billowing into the air.

Local officials told Russian news agencies that some 2,000 people were evacuated from the area as a precaution.

It was the second Crimea munitions dump explosion in a week. On August 9, ammunition detonated at a military airfield, killing one person and wounding several more.

Russia had indicated that the airfield was not targeted by Ukrainian forces and Ukraine also denied responsibility, but experts said satellite imagery pointed to a likely attack, with several Russian warplanes destroyed.  

On Tuesday, top Ukrainian presidential aide Mykhailo Podolyak said the latest blasts in Dzhankoi were a "reminder" that "Crimea occupied by Russians is about warehouses explosions and high risk of death for invaders and thieves".

Russia annexed Crimea in 2014 in the wake of massive nationwide street demonstrations in Ukraine that led to the ouster of a Kremlin-friendly president.

Those protests precipitated fighting between the army and Moscow-backed separatists in eastern Ukraine, which laid the groundwork for Moscow's full-scale assault on February 24 this year.