Russian forces are succeeding in the war effort in Crimea, the Russian-backed governor tells the state-run news agency TASS, except for the skies, which are filled with Ukrainian drones.

"Our main threat to Crimea is drones; everything else is under full control," Gov. Sergey Aksyonov said.

While military drones range in size, with some being quite large, the assault on Crimea appears to be coming from small drones like average citizens typically buy, Task & Purpose reports.

What the drones lack in size, they make up for in stealthiness and numbers.

The UAVs "are small in size, have a powerful battery, and sometimes they go not one by one, but in a wave," Aksyonov said.

Drone attacks in Crimea, which was annexed by Russia in 2014, have spiked recently.

Russian air defenses shot down a group of drones in western Crimea in August; and in late November, they stopped another set of drone attacks. One of them allegedly was targeting a regional power station.

And Ukrainian drone boats attacked Russian warships in the Crimean port of Sevastopol in October, putting Russian forces on edge in the area, Task & Purpose said.

Aksyonov "is implying that, apart from a few high profile cases, there have been other attacks, although he's hinting that air defenses are capable of handling it," Sam Bendett, an expert on unmanned systems at the Center for Naval Analyses, told Task & Purpose.

The Ukrainian drone campaign is succeeding in putting pressure on Russian forces in Crimea "if [Aksyonov] has to say it publicly on Russian state media,” Bendett added.

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