Ukraine pressed on with a major cross-border incursion into Russia, where state media and local officials on Friday reported a fire at a military airfield and "massive" drone attacks hundreds of kilometres from the border.

The Ukrainian offensive in the Kursk region over the past few days appears to be the most significant attack on Russian soil since the war in Ukraine began in 2022. It involved around 1,000 troops and more than two dozen armoured vehicles and tanks, according to the Russian army.

Kyiv has not officially taken responsibility for the operation, but Ukrainian President Volodymyr Zelensky said in his evening address on Thursday that Russia needed to "feel" the consequences of its invasion.

"Russia brought the war to our land and should feel what it has done," Zelensky said, without directly referring to the offensive.

Early Friday, official Russian news agencies TASS and RIA Novosti reported a fire at a military airfield in the neighbouring Lipetsk region citing the local emergencies ministry directorate, though neither outlet offered a cause.

The reports came just hours after regional governor Igor Artamonov announced on Telegram at around 3:00 am (0000 GMT) that Lipetsk had "been subjected to a massive UAV (unmanned aerial vehicle) attack", later adding a local power facility was damaged.

In a subsequent message, Artamonov urged residents to ignore calls on social media to leave Lipetsk -- saying they were "spread by the enemy in order to sow panic" -- only to reverse course less than an hour later.

"To eliminate the consequences of the detonation of explosive objects, a state of emergency is introduced in Lipetsk municipal district," he said in a post at around 4:00 am, listing evacuation orders for four settlements on the outskirts of Lipetsk city.

"Temporary accommodation points and transport are being prepared."

Artamonov said preliminary reports suggested at least six people had been wounded as a result of the attack.

He later announced around 7:00 am that the red threat level for the city had been lifted.

Russia's defence ministry said its forces shot down 75 Ukrainian drones overnight including 26 in the Belgorod region which borders Ukraine, 19 over Lipetsk, seven over Kursk, and 13 over the annexed Crimean peninsula and surrounding Black Sea.

Seven nautical drones headed for Crimea were also destroyed, it added.

- Cross-border gains -

Lipetsk city is about 330 kilometres (210 miles) from the Ukrainian border with Russia's Kursk region, where pro-Kyiv forces for days have been waging an offensive on Russian territory.

The independent US-based Institute for the Study of War said Ukraine had made significant territorial gains since the push began on Tuesday.

"Geolocated footage and Russian claims indicate that Ukrainian forces continued rapid advances further into Kursk Oblast on August 8 (Thursday), and Ukrainian forces are reportedly present in areas as far as 35 kilometers from the international border with Sumy Oblast" in Ukraine, the institute said in its daily campaign assessment.

It cautioned, however, that Ukrainian forces "most certainly do not control" all of that territory.

Russia's defence ministry said Thursday that its troops were "continuing to destroy" armed Ukrainian units and were using air strikes, rocket and artillery fire to try to push them back.

It said it had rushed in reserves and was "thwarting attempts to break through" deeper into Kursk.

Russian President Vladimir Putin has called the incursion a "large-scale provocation" by Kyiv, and Russia's top general vowed on Wednesday to crush it.

The US State Department has expressed support for Kyiv without directly commenting on the operation.

AFP

A photo released by a local official shows damage in the Russian town of Sudzha as Ukraine presses an incursion into Russian territory © - / Governor of Kursk Region/AFP

Ukraine presses on with offensive as Russia reports airfield fire