Mr Putin met with top defence and security officials to discuss Ukraine's "indiscriminate shelling of civilian buildings, houses, ambulances with various types of weapons". He instructed the Cabinet to coordinate support for the Kursk region. The fighting is about 500km from Moscow.

At an online meeting, Russian military chief of staff Valery Gerasimov told Mr Putin that about 100 Ukrainian soldiers had been killed in the fighting and more than 200 were wounded, Russian news agencies reported.

Meanwhile, Russian Foreign Ministry spokeswoman Maria Zakharova said Ukrainian shelling had killed at least two people – a paramedic and an ambulance driver – and injured 24.

While Russian officials insist they are fighting back against cross-border raids for a second day, Ukrainian officials remain silent about the scale of the operation.

The head of the Kursk region has urged residents to donate blood due to the intense fighting. “Over the past 24 hours, our region has heroically resisted attacks” from Ukrainian militants, acting governor Alexei Smirnov said, adding that all emergency services were on high alert.

Authorities evacuated more than 200 people from shelled areas, while thousands more left in private vehicles, Mr Smirnov said.

If confirmed, the cross-border offensive would be one of Ukraine's largest since the Russia-Ukraine conflict broke out in February 2022, and an unprecedented deployment of Ukrainian military units.

Russian forces have quickly repelled previous cross-border incursions, but they have still caused damage.

The Russian Defense Ministry said on August 6 that up to 300 Ukrainian troops, supported by 11 tanks and more than 20 armored fighting vehicles, had crossed the border into Russia and suffered heavy losses.

On August 7, the report said the army and border guards "continued to destroy Ukrainian military units in areas along the border in the Kursk region." The ministry said Russian forces, supported by artillery and warplanes, "did not allow the enemy to advance deeper into the territory of the Russian Federation."

The Kursk region's border with Ukraine is 245 km long, allowing saboteurs to launch quick attacks and capture some territory before Russia deploys reinforcements.

Hoai Phuong (according to TASS, AP)