KYIV – Hundreds of people were evacuated from areas near the Russian border in Ukraine's Kharkiv region, its governor said on Saturday, a day after Moscow launched a surprise ground offensive.

Russian forces made small advances in the area it was pushed back from nearly two years ago, the latest in a series of gains as Ukrainian forces find themselves outgunned and outmanned.

"A total of 1,775 people have been evacuated," Kharkiv Gov. Oleg Synegubov wrote on social media.

He reported Russian artillery and mortar attacks on 30 settlements over the past 24 hours.

Ukrainian President Volodymyr Zelenskyy said on Saturday a "fierce battle" was underway in Kharkiv, adding that "we must disrupt Russian offensive operations and return the initiative to Ukraine."

The region has been mostly under Ukrainian control since September 2022.

A senior Ukrainian military source said Russian forces had advanced 1 kilometer (0.6 miles) into Ukraine and were trying to "create a buffer zone" in Kharkiv and the neighboring Sumy region to prevent attacks on Russian territory.

Ukrainian forces have multiplied attacks inside Russia and Russian-held areas of Ukraine, particularly on energy infrastructure.

On Saturday, Moscow-installed authorities in the Russian-occupied Luhansk region in eastern Ukraine said at least three people were killed by a Ukrainian strike with US-made missiles on an oil depot.

Luhansk Gov. Leonid Pasechnik said the strike "enveloped the oil depot in fire and damaged surrounding homes."

"The death toll has risen to three, and eight more people are in hospital," he said on social media.

Officials in Kyiv had warned for weeks that Moscow might try to attack its northeastern border regions, pressing its advantage as Ukraine struggles with delays in Western aid and manpower shortages.

Ukraine's military said it had deployed more troops, and Zelenskyy said Ukrainian forces were using artillery and drones to thwart the Russian advance.

"Reserve units have been deployed to strengthen the defense in this area of the front," it said.

The US-based Institute for the Study of War (ISW) said on Friday that Russia had made "tactically significant gains."

But the main aim of the operation was "drawing Ukrainian manpower and materiel from other critical sectors of the front in eastern Ukraine," it said.

The ISW said it did not appear to be "a large-scale sweeping offensive operation to envelop, encircle and seize [the city of] Kharkiv," Ukraine's second largest.