Russian authorities are seeding clouds to try to induce rain over an epidemic of forest fires in Siberia.

The operations come after Donald Trump offered Vladimir Putin help fighting the blazes.

An Antonov An-26 turboprop flew to northern Irkutsk region on Thursday to fire exploding shells of silver iodide into “clouds suitable for artificial rain induction operations,” the state aerial forest conservation brigade said. Fires in three districts are located under rain-bearing clouds, it said.

After refuelling, the plane will fly into the Krasnoyarsk region to seed clouds over fires in a district there.

Silver iodide shells have been shot over some 100 fires since the start of July, resulting in medium and heavy rains in two out of every three attempts, the brigade claimed. It has also deployed 500 firefighters to assist locals in four regions.

Russia is in the grips of one of the worst fire seasons in recent years, with more than 12,000 square miles burning as of late July. The sun has turned red from smoke in some cities, and dangerous levels of air pollution have been reported in Chelyabinsk, Tomsk and Novosibirsk. Russia doesn't extinguish most fires unless they threaten populated areas.