WASHINGTON (AP) — The White House said Thursday that the U.S. has evidence that Iranian troops are “directly engaged on the ground” in Crimea supporting Russian drone attacks on Ukraine’s infrastructure and civilian population.

National Security Council spokesman John Kirby told reporters that Iran has sent a “relatively small number” of personnel to Crimea, a part of Ukraine unilaterally annexed by Russia in contravention of international law in 2014, to assist Russian troops in launching Iranian-made drones against Ukraine.

“The information we have is that the Iranians have put trainers and tech support in Crimea, but it’s the Russians who are doing the piloting,” Kirby said.

The U.S. first revealed this summer that Russia was purchasing Iranian unmanned aerial vehicles to launch against Ukraine. Iran has denied selling its munitions to Russia.