Russian forces launched an armoured ground attack on Friday near Ukraine’s second city of Kharkiv in the northeast of the country and made limited gains, opening a new front in a war that has long been waged in the east and south.

Ukraine sent reinforcements as fighting raged in the border areas of the region, the defence ministry said, adding that Russia had pounded the frontier town of Vovchansk with guided aerial bombs and artillery.

“At approximately 5 a.m., there was an attempt by the enemy to break through our defensive line under the cover of armoured vehicles,” the ministry said.

“As of now, these attacks have been repulsed; battles of varying intensity continue.”

A senior Ukrainian military source who declined to be named said Russian forces had pushed 1 km (0.6 mile) inside the Ukrainian border near Vovchansk.

The source said Russian forces were aiming to push Ukrainian troops as far back as 10 km inside Ukraine as part of an effort to create a buffer zone, but that Kyiv’s troops were trying to hold them back.

There was no immediate comment from Russia.

Ukrainian President Volodymyr Zelenskiy told a press conference in Kyiv that Ukrainian forces had been prepared to meet the assault, but said Moscow could send more troops to the area.

Ukraine chased Russian troops out of most of the Kharkiv region in 2022, following Russia’s full-scale invasion in February of that year. But after weathering a Ukrainian counteroffensive last year, Russian forces are back on the offensive and slowly advancing in the Donetsk region that lies further south.

Ukrainian concerns grew in March over the Kremlin’s intentions in the Kharkiv region when Russian President Vladimir Putin called for the creation of a buffer zone inside Ukrainian territory. He said this was needed to protect Russia from shelling and border incursions.

Since then, Kharkiv, which is particularly vulnerable because of its proximity to Russia, has been hammered by air strikes that have damaged the region’s power infrastructure.

In Vovchansk, a Kharkiv region border town with a pre-war population of 17,000 that has dwindled to a few thousand, authorities said the settlement and surrounding areas were under heavy shelling.

Authorities were helping civilians evacuate, Tamaz Gambarashvili, head of the Vovchansk military administration, told Hromadske radio.

More than two years after its invasion, Russia has the battlefield momentum and Ukraine faces shortages of manpower and stocks of artillery shells and air defences.