Three local witnesses told Reuters on Tuesday they had heard loud explosions and seen black smoke billowing from the direction of a Russian military airbase in Novofedorivka in western Crimea.
Videos supposedly captured at the scene, some of them published on social networks, showed a column of smoke in the area. The videos could not be immediately verified.
Over the course of a minute, at least 12 explosions of varying intensity were heard, according to two witnesses. Three of them were especially strong and caused sparks and smoke.
Russia leased the naval port of Sevastopol, home to its Black Sea Fleet, from kyiv for decades, but annexed the entire Ukrainian peninsula in 2014.
The peninsula, which remains under Russian control, has been spared heavy shelling and shelling that has been taking place in other parts of eastern and southern Ukraine since February 24, when President Vladimir Putin ordered the entry of the Russian armed forces in Ukraine.