London, Aug 12 (IANS): Explosions at the Saki military airfield on Ukraine's occupied Crimean Peninsula have significantly weakened the naval aviation of Russia's Black Sea Fleet, the UK's Ministry of Defence said on Friday.

At least eight aircraft were destroyed or damaged, according to the Ministry's intelligence update.

"The loss of eight combat jets represents a minor proportion of the overall fleet of aircraft Russia has available to support the war.

"However, Saki was primarily used as a base for the aircraft of the Russian Navy's Black Sea Fleet," it said.

The cause of Tuesday's explosions remains unclear, it added, but the mushroom-shaped columns of smoke seen on witness videos were most likely from up to four areas where ammunition was stored unprotected.

According to the Ministry, the airfield itself should still be usable despite considerable damage.

While Russia has played down the explosions, a top Ukrainian adviser denied that Kiev was responsible.

It is likely, however, that Russia will adjust its assessment of Crimea's security.

Until now, the Ukrainian peninsula, occupied by Russia since 2014 after a referendum which the international community sees as illegitimate, had probably been classified as a safe hinterland.