Russia launched a cross-border ground offensive into Ukraine's northeast Kharkiv region and civilians were being evacuated amid the fighting, Ukrainian officials said Friday.
Ukraine pushed back Russian forces from most of Kharkiv region in late 2022, but Moscow is now back on the offensive there as Kyiv's troops struggle with ammunition and manpower shortages.
"At approximately 5:00 am (0200 GMT), the enemy attempted to break through our defence line under the cover of armoured vehicles," the Ukrainian defence ministry said.
Ukraine said that it had repelled Russia's incursion but that "fighting of varying intensity" was ongoing and that Russia had launched aerial strikes into an area near the border.
A high-ranking Ukrainian military source said Russia had advanced into Ukraine by one kilometre (.6 miles) , and was trying to "create a buffer zone" to prevent attacks into Russian territory.
If Russia's advances are confirmed, it would represent the Kremlin's biggest land offensive in the region since it sent thousands of troops across the border in February 2022.
The Russian defence ministry has not provided any comment but Russian military bloggers suggested active fighting was taking place.
A local official said there was "massive shelling" of the town of Vovchansk, which has a population of 3,000 people, and evacuations were underway there and in nearby areas.
At least two people were wounded in Russian shelling of the town in the morning, regional police said.
"Enemy shelling from various types of weapons has been intensifying in Kharkiv region in the northern direction for the last day," regional governor Oleg Sinegubov said.
"In Kharkiv region, evacuation routes have been developed since 2022, and a system of humanitarian aid distribution, temporary resettlement," he said.
Vitaliy Ganchev, the Russian-installed head in the region, confirmed there was fighting near the border and urged civilians to take shelter.
"There is fighting on several parts of the line of contact, including in the border areas of Kharkiv region," he said on Telegram.
"In this regard, I ask residents living in these areas to be careful and not to leave shelters without an urgent need," he added.
Russia's defence ministry said it had captured at least two villages in the region this week, pressing its advantage against outgunned and outmanned Ukrainian troops.
Russian President Vladimir Putin warned in March he was considering creating a buffer zone in Ukrainian territory adjoining Belgorod, a Russian region frequently targeted by Ukrainian shelling.
Ukrainian shelling on Russian border villages killed at least two people on Thursday, the governors of Russia's Belgorod and Kursk border regions said.
Pro-Ukrainian militias also claimed earlier this year to have stormed Russia's frontier in a series of brazen raids, a source of embarrassment for the Kremlin.
