The United States said Thursday that Iranian military trainers had been sent to Crimea to assist Russian forces using Iranian-made drones to attack targets in Ukraine, adding a new international element to a war that has already worsened some geopolitical tensions.

Ukrainian citizens endured the first day of nationwide scheduled power outages since the war began eight months ago so repairs could be made to damaged or destroyed energy plants as winter approaches.

"We can confirm that Russian military personnel based in Crimea have been piloting Iranian UAVs and using them to conduct kinetic strikes across Ukraine, including in strikes against Kyiv in recent days," U.S. State Department spokesman Ned Price told a daily briefing with reporters, referring to unmanned aerial vehicles, or drones.