Russian forces in northeastern Ukraine, already pushed back to near the Russian border, appeared Thursday to be launching a new counteroffensive as the three-month-old war morphed into what some Western officials described as a 'scrap' with no end in sight.

Authorities in Ukraine's second-biggest city, Kharkiv, said Russian shelling had killed at least seven civilians and wounded 17 others, while heavy fighting raged north and east of the city.

Witnesses in Kharkiv also reported hearing repeated explosions as Russian forces appeared to try to fortify positions north of the city.

Paramedics and emergency workers provide medical care to a man wounded as a result of shelling in Kharkiv, May 26, 2022, on the 91st day of Russia's invasion of Ukraine.

Russian forces near Kharkiv had been steadily pushed from the city to close to the Russian border following a Ukrainian counteroffensive earlier this month. But officials said it appeared Moscow had decided to push back.

'It's too early to relax,' said Kharkiv region Governor Oleh Synehubov. 'The enemy is again insidiously hitting the civilian population, terrorizing them.'

Russian officials have not yet commented on the developments near Kharkiv, though the Russian military's social media feeds touted continued success against Ukrainian forces, including in the Donbas region.

A local resident sits at a destroyed house in Vilkhivka village, near Kharkiv, on May 25, 2022, amid Russia's invasion of Ukraine.

A senior U.S. defense official said Thursday that despite reports of increased fighting around Kharkiv, there had been 'no major changes' on the ground.

'We still assess that Ukrainian forces have continued to push Russian forces further away [from the city],' the official said, briefing reporters on the condition of anonymity in order to discuss intelligence.

'It's a range of a few kilometers to more than 10 kilometers within the Russian border,' the official added.

But in other parts of eastern Ukraine, Russia was able to make what the official described as 'incremental gains,' including in the city of Popasna and in Sievierodonetsk, the easternmost city under Ukrainian control.

A woman runs to cover from shelling in a recently retaken village north of Kharkiv, eastern Ukraine, May 25, 2022, amid the Russian invasion of Ukraine.

'We believe that Russian forces have been able to seize most of northeastern Sievierodonetsk,' the U.S. defense official said. 'But they haven't been able to cut it completely off because the Ukrainians are still fighting over it.'

Ukrainian officials on Thursday acknowledged Russia was making a push to surround its troops fighting in the east with advances both on Sievierodonetsk and the nearby city of Lysychansk.

'Russia has the advantage, but we are doing everything we can,' General Oleksiy Gromov, with Ukraine's general staff, told Reuters.

'It is clear that our boys are slowly retreating to more fortified positions - we need to hold back this horde,' added Luhansk province Governor Serhiy Gaidai.

In this handout photo provided by the Ukrainian Presidential Press Office, Ukrainian President Volodymyr Zelenskyy meets with Finnish Prime Minister Sanna Marin in Kyiv, Ukraine, May 26, 2022.

In a show of support Thursday, Finnish Prime Minister Sanna Marin visited Kyiv, plus the towns of Irpin and Bucha, the scene of alleged Russian war crimes.

'We, Finland, support all the actions of the International Criminal Court to consider these crimes, collect evidence for future proceedings and convict Russia,' Marin said following a meeting with Ukrainian President Volodymyr Zelenskyy.

Zelenskyy, in a post on social media, thanked Finland for its support.

'Finland's military assistance is very valuable,' he wrote. 'Weapons, sanctions policy and the unity of our partners in the issue of Ukraine's accession to the EU - this is what can provide strength in the defense of our land.'

Despite the back-and-forth nature of the fighting and Russia's superior numbers, Western officials continue to laud Kyiv for mounting a stiff resistance and for making good use of security assistance that continues to pour into the country.

Ukraine's military has likewise shared some optimism about its ability to counter Russian forces, claiming it has killed 29,600 Russian forces since the start of the February 24 invasion.

U.S. estimates of Russia's material losses, shared Thursday, are slightly more conservative than those coming from Kyiv. But the senior U.S. defense official said Russia has lost about 1,000 tanks, almost 40 aircraft, more than 50 helicopters and 350 pieces of artillery.

The official declined to share any estimates on Russian casualties but said the losses have not been insignificant, though things have changed since the start of the war.

'The Russians lose soldiers every day, but it's a different ... number based on the kind of fighting we're seeing,' the official said. 'The fighting is now largely over smaller pieces of turf with smaller units.'

Russia's military Thursday issued its own estimates of Ukraine's losses, saying its forces had so far destroyed 179 planes, 127 helicopters, more than 1,000 drones, hundreds of anti-aircraft systems, and more than 1,600 Ukrainian artillery and mortar systems.

In the meantime, key Western leaders Thursday emphasized the need to continue backing Ukraine.

Russian President Vladimir Putin 'must not win his war, and I am convinced he will not win,' German Chancellor Olaf Scholz said at the World Economic Forum in Davos, Switzerland.

He also said Russia should not be allowed to dictate the terms of a peace agreement.

'Ukraine will not accept this, and neither will we,' Scholz said.

Separately, Kyiv Mayor Vitali Klitschko told the forum Ukraine was the 'key for freedom in the world.'

'We're defending not just our family and our children, we're defending you, because we have the same values,' Klitschko said, adding that Russia would go as far as it was allowed to go.

Some information for this report came from The Associated Press, Agence France-Presse and Reuters.