Ukraine and Russia are intensifying attacks on each other's energy infrastructure.

Ukraine's air force said Russian forces had staged assaults with 27 drones and nine missiles across the country through Thursday. They said all the drones and five missiles had been shot down.

Ukraine's energy ministry officials said energy facilities, including a thermal power plant, in four regions had been damaged and three engineers were injured.

A power utility said its thermal plant had suffered a large-scale attack for the seventh time in three months.

The Russian military began stepping up attacks on Ukraine's energy infrastructure in March, forcing rolling blackouts across the country due to serious power shortages.

Russia's defense ministry said its forces had downed 15 Ukrainian unmanned aerial vehicles through Thursday.

The governor of the western region of Tambov and the head of a southern republic said the drone attacks had caused fires at oil storage depots.