Ukraine pressed on with a major cross-border incursion into Russia on Friday, also launching a significant air attack on a Russian airfield hundreds of kilometres behind the front lines.
The Ukrainian offensive into Russia's western Kursk region, launched Tuesday, appears to be the most significant attack on Russian soil since Moscow invaded in February 2022.
Russia says around 1,000 Ukrainian troops and more than two dozen armoured vehicles and tanks were involved in the initial attack, though it has since claimed to have destroyed many more pieces of hardware.
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.
Ukraine said Friday it had carried out a massive air strike on a Russian military base in the Lipetsk region, around 280 kilometres (175 miles) from the Russia-Ukraine border.
The local Russian governor Igor Artamonov reported a "massive" drone attack overnight and Russian state news agencies said the airfield was on fire.
"Last night, the Ukrainian Defence Forces attacked the Lipetsk airfield," Ukraine's General Staff said in a post on Telegram.
It said it had struck "warehouses containing guided aerial bombs and a number of other facilities" and that a "massive fire broke out" with "multiple detonations."
Artamonov cancelled several public events in the region and issued evacuation orders for districts close to the air base.
Russia's defence ministry said it destroyed 75 Ukrainian drones overnight, including 19 over the Lipetsk region and seven over Kursk, where Ukraine's four-day incursion has focused.
Several nautical drones headed for the annexed peninsula of Crimea were also destroyed, it said.
Ukraine's surprise offensive into the Kursk region has appeared to catch Russia off guard, and triggered harsh criticism of the defence ministry by influential military bloggers.
Senior Kyiv officials have stayed tight-lipped over the incursion, though some, including Zelensky have appeared to justify the attack.
"Russia brought the war to our land and should feel what it has done," Zelensky said on Thursday, without directly referring to the offensive.
"Everyone can see that the Ukraine army knows how to surprise, and knows how to achieve results," he said in another apparent reference to the incursion without explicitly mentioning it.
Moscow has also not presented detailed information on the extent of the Ukrainian incursion.
But the independent US-based Institute for the Study of War said Ukraine had made significant territorial advances.
"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 the Kursk region.
Russian President Vladimir Putin has called the incursion a "large-scale provocation" by Kyiv, and Russia's top general vowed to crush it.
In a meeting with the local governor on Thursday, Putin said he needed to show "courage" and that Moscow was marshalling all state resources to deal with the situation.
The health ministry said 66 civilians were wounded, including nine children, in the first three days of the Ukrainian incursion.
On the first day of the assault, Kursk regional governor Alexei Smirnov said five civilians were killed.
Thousands have been evacuated from the region, with Russia putting on an extra train from the regional capital of Kursk to Moscow for those looking to leave.
Ukraine has also evacuated several thousand from the Sumy region, which sits across the border from Kursk.
Two people were killed there over the last 24 hours, Ukraine's interior ministry said Friday.
The US State Department and European Union have expressed support for Kyiv's right to defend itself from Russian aggression, without directly commenting on the operation.
