Ukrainian air defences have shot down 3,605 of the drones, he said in televised comments that gave an idea of the scale of Russia's aerial onslaught on Ukraine in two years of war since the full-scale invasion on Feb. 24, 2022.

Ihnat said small mobile teams of drone hunters were now bringing down most of the drones fired at Ukraine, including Iranian-made Shaheds, and their success rate was high.

In the latest overnight attack on Thursday, eight out of 10 Russian-launched drones were shot down over four Ukrainian regions, Ihnat said.

After two years of war, Moscow controls almost a fifth of Ukrainian territory including the Crimea peninsula it annexed in 2014 although the front lines have largely stagnated in the last 14 months.

Ukraine's defences have been strengthened by deliveries of advanced air defence systems from Western allies, including U.S. Patriots. Ihnat did not provide overall numbers for such assistance and Ukrainian officials have said repeatedly that they need more weapons from abroad to support the war effort.

The overall number of Ukrainian military casualties is also not made public in a war that has killed or wounded hundreds of thousands of people, destroyed cities, towns and villages, forced millions from their homes and placed hundreds of thousands more under occupation.

Ihnat said Russia had prioritised targets such as agriculture facilities, port infrastructure, weapons production and the oil and gas sector this winter - a shift in tactics after focusing primarily on the energy system last winter, causing long blackouts for millions of people.

Russia says it fires only on military targets but has acknowledged targeting energy infrastructure.