MOSCOW, Aug 17 (Reuters) - Russia has replaced the commander of its Crimea-based Black Sea Fleet after a series of explosions rocked the peninsula it annexed in 2014 and had previously seen as a secure rear base for its war in Ukraine.

Moscow blamed saboteurs for blasts that engulfed an ammunition depot in northern Crimea on Tuesday (Aug 16). Plumes of smoke were later seen rising at a second Russian military base in central Crimea, Russia's Kommersant newspaper said.

Ukraine has not officially taken responsibility but has hinted at it. The apparent Ukrainian capability to strike deeper into Russian-occupied territory, either with some form of weapon or with sabotage, indicates a shift in the conflict. Blasts destroyed warplanes at a Russian naval airbase in Crimea last week.

On Wednesday, Russia's RIA news agency cited sources as saying the commander of its Black Sea fleet, Igor Osipov, had been replaced with a new chief, Viktor Sokolov.

If confirmed, the move would mark one of the most prominent sackings of a military official so far in a war in which Russia has suffered heavy losses in men and equipment.

State-owned RIA cited the sources as saying the new chief was introduced to members of the fleet's military council in the Crimean port of Sevastopol.

The Black Sea Fleet, which has a revered history in Russia, has suffered several humiliations since President Vladimir Putin launched the invasion of Ukraine - which Moscow calls a "special military operation" - on Feb 24.

In April, Ukraine struck its flagship, the Moskva, a huge cruiser, with Neptune missiles. It became the biggest warship to be sunk in combat for 40 years.