RUSSIA’S Ministry for Emergencies declared the situation in the Kursk region a “federal level” emergency today, four days after hundreds of Ukrainian troops poured over the border in what appeared to be Kiev’s biggest attack on Russian soil since the war began.

“The operational situation in the Kursk region remains difficult,” Kursk acting governor Alexei Smirnov said on the messaging app Telegram.

Social services and civic associations are providing assistance to people forced to flee their homes by the fighting, he said. The last Russian figure for evacuations in Kursk was 3,000.

Little reliable information about the surprise Ukrainian operation has emerged, and its strategic aims are unclear. Ukrainian officials have refused to comment specifically about the incursion, which is taking place about 320 miles south-west of Moscow.

But a top adviser to Ukraine President Volodymyr Zelensky said on Thursday that border region attacks will cause Russia to “start to realise that the war is slowly creeping inside of Russian territory.”

The assault came as the Ukrainian army toils to hold at bay an intense Russian push at places on the front line in eastern Ukraine, especially in the Donetsk region.

Russian President Vladimir Putin has made clear he wants to capture the parts of Donetsk that the Kremlin’s forces don’t already occupy.

Russia declares federal level emergencies when there are more than 500 victims or damage exceeds 500 million rubles (about £4.4m).

A Russian Defence Ministry statement said only that the military “continues to repel the attempted invasion” and is responding with air strikes, artillery and troops on the ground.

Ukraine has also kept up its strategy of hitting rear areas with long-range drones, targeting military sites, oil refineries and other infrastructure.

Ukrainian drones attacked Russia’s Lipetsk region, which is about 180 miles from the Ukraine border, during Thursday night, authorities said.

The regional emergencies ministry in Lipetsk said there was a fire at a military airfield where fighter planes including MiG-29s and Su-34s reportedly are based.

Lipetsk governor Igor Artamonov said that unspecified electrical infrastructure was damaged and nine people were wounded in the attack.