Update(10:16ET): Within an hour of the first videos hitting social media and widely circulating, Russia's defense ministry has said the large explosion at its Crimean Saky Airbase was not the result of an airstrike or shelling. The statement said ammunition stored at the airfield detonated, but the cause of what ignited the storage depot is still unknown and being investigated. Russian state media has published the following English-language statements of the defense ministry:

The Russian Defense Ministry has reacted to reports of explosions near the town of Novofedorovka in Crimea, saying that a detonation of several rounds of air-launched ammunition had taken place at the Saki airfield located not far from the town.

The detonated ammunition was stored at the airfield's bunded storage area, the ministry said, adding that the ensuing blasts did not result in casualties or damage to aircrafts. The resulting fire is in the process of being put out, the Defense Ministry elaborated.

The ammo's detonation did not happen due to shelling or an airstrike on the airport, the ministry underscored.

Casualties are being reported, after initial Russian media reports there were no known casualties in the immediate aftermath of the explosion:

HEAD OF CRIMEA HEALTH DEPARTMENT: FIVE PEOPLE INCLUDING ONE CHILD INJURED BY BLAST IN CRIMEA - TASS

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A massive explosion erupted Tuesday deep inside Crimea at Russia's Saky Airbase in Novofedorivka, which lies some 200km from front line fighting in Ukraine, immediately giving rise to speculation that this could have been a Ukrainian long-range missile strike.

Few details are confirmed thus far, only that a multiple-stories high fireball and smoke was filmed from many angles engulfing the Russian military airbase.

Local social media reports cited eyewitness accounts which said ambulances and emergency crews are speeding toward the site of the large explosion.

Nearby beachgoers in Crimea looked on stunned, given the ongoing Ukraine war has never before reached the environs of the territory which Russia controversially formally took over in 2014 following the so-called "Crimea crisis" and referendum.

Some Ukraine war commentators were quick to speculate that given the site of the explosion apparently by unknown munitions is some 200km away from front lines, this means...

either Russia “had an accident” or Ukraine has some long range rockets.

An initial Russian defense ministry statement cited no casualties...

RUSSIA'S DEFENCE MINISTRY: NO CASUALTIES AFTER BLAST AT RUSSIAN MILITARY AIRBASE AT NOVOFEDORIVKA, CRIMEA - RIA

The airbase lies deep within the Crimean peninsula.