Russian forces launched an armoured ground attack on Friday near Ukraine’s second city of Kharkiv in the northeast of the country and made small inroads, 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.

“Russia has begun a new wave of counteroffensive actions in this direction,” Ukrainian President Volodymyr Zelenskiy told a news conference in Kyiv. “Now there is a fierce battle in this direction.”

Ukraine had warned of a Russian buildup in the area, potentially signalling preparations for an offensive or a ploy to divert and pin down Ukraine’s overstretched and outnumbered defenders. It was unclear if Moscow would develop the attack.

In its evening battlefield update, the Ukrainian General Staff said for the first time that Russia was also building up forces to the north of Kharkiv near the Ukrainian regions of Sumy and parts of Chernihiv.

Zelenskiy has said Russia could be preparing a big offensive push this spring or summer. Kyiv’s forces were prepared to meet Friday’s assault, but Moscow could send more troops to the area, he told reporters.

The Ukrainian defence ministry said Russia launched an armoured assault at around 5 am In an update at 10 pm., the General Staff said battles were continued to prevent Russian offensive efforts to advance in the Kharkiv region.

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.

The White House said the United States had been coordinating closely with Ukraine on Russia’s Kharkiv offensive.

“It is certainly possible that the Russians are setting themselves up for a larger assault on Kharkiv,” White House national security spokesperson John Kirby told reporters.

Top Ukrainian officials have repeatedly said they do not believe Russia has the force capacity available to launch a successful operation to capture the city of Kharkiv, home to 1.3 million people.The General Staff said battles raged for control of three frontier villages - Strilecha, Pylna and Borysivka - that were already seen as in a “grey area” of control.

“Counter-offensive measures continue in the direction of the settlements of Lyptsi and Vovchansk. The enemy is using infantry and equipment,” it said on the Telegram app.

Military spokesperson Nazar Voloshyn said fighting was still raging in the evening and that the situation was dynamic. He said he believed Moscow’s operation aimed to draw troops to Kharkiv from the east where Russia is focusing its offensive.

There was no immediate comment from Moscow.

At least two civilians were killed and five were injured during heavy shelling of border settlements, said Oleh Synehubov, governor of Kharkiv region.

“All the enemy can do is to attack in certain small groups, you can call them sabotage and reconnaissance groups or something else, and test the positions of our military,” he said.

In Vovchansk, a town with a pre-war population of 17,000 that has dwindled to a few thousand, authorities said they were helping civilians evacuate from the settlement and surrounding areas due to the heavy shelling.

In his evening address, Zelenskiy said his top commander Oleksandr Syrskyi had reported to him that “heavy fighting” was taking place all along the more than 1,000-km (600-mile) front line.

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.

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.