A employee stands next to a facility of the Darnytsia Car Repair Plant damaged by missile strikes, as Russia's attacks Ukraine in continues, in Kyiv, Ukraine June 5, 2022.
A employee stands next to a facility of the Darnytsia Car Repair Plant damaged by missile strikes, as Russia's attacks Ukraine in continues, in Kyiv, Ukraine June 5, 2022. Reuters / VALENTYN OGIRENKO

Ukrainian and Russian troops fought street-by-street to win control of the industrial city of Sievierodonetsk on Monday in the pivotal battle of the Kremlin's eastern Ukraine offensive.

Which side had the upper hand was unclear as the hours passed. Russian forces had the numerical advantage but Ukraine had "every chance" to fight back, President Voldymyr Zelenskiy said after a regional official suggested Kyiv had lost ground.

Ukraine's defence ministry said Russia was throwing troops and equipment into its drive to capture Sievierodonetsk, the largest remaining Ukrainian-held city in the Donbas region's Luhansk province.

The Ukrainian defenders had over the weekend pushed back the Russians just as they appeared to be on the verge of victory. But the Ukrainian position had again become more perilous on Monday morning, Luhansk governor Serhiy Gaidai told state television.

"Our defenders managed to undertake a counter-attack for a certain time, they liberated almost half of the city. But now the situation has worsened a little for us again," Gaidai said.

City mayor Oleksandr Stryuk said street fighting was raging and neither side was preparing to withdraw.

"We have focused enough forces and resources there to beat back attacks on the city," Stryuk told Ukrainian television.

Both sides say they have inflicted huge casualties on each other.

The city has become the main target of the Russian offensive in Ukraine's Donbas region - made up of Luhansk and Donetsk provinces - as the Kremlin's invasion of the country grinds on in a war of attrition that has seen whole cities laid waste by Russian artillery bombardments.

Russia says it is on a mission to "liberate" the Donbas after Ukraine pushed its troops back from the capital Kyiv and Ukraine's second biggest city Kharkiv in the war's early stages.

Ukrainian President Volodymyr Zelenskiy sought to rally his troops on Sunday with a visit to two cities close to the front lines.

"What you all deserve is victory - that is the most important thing. But not at any cost," Zelenskiy, wearing his trademark khaki T-shirt, said in a video.

Zelenskiy said he had travelled to Lysychansk, south of Sievierodonetsk, and Soledar - rare outings for him outside of Kyiv since the start of the Russian invasion on Feb. 24.

PUTIN WARNING

In a boost for Kyiv, Britain said it would supply Ukraine with multiple-launch rocket systems that can strike targets up to 80 km (50 miles) away. The systems would give the Ukrainians the more precise, long-range firepower needed to reach Russian artillery units, a key component of Moscow's battle-plans.

The British move was coordinated with the United States, which last week pledged to supply Kyiv with advanced rocket systems.

Russian Foreign Minister Sergei Lavrov said Moscow would respond to Western deliveries of long-range weapons to Ukraine by pushing Ukrainian forces further back from Russia's border.

On Sunday, President Vladimir Putin said Russia would strike new targets if the West supplied longer-range missiles to Ukraine. The same day, Russian missiles hit Kyiv for the first time in more than a month. Ukraine said the strike hit a rail car repair works, while Moscow said it had destroyed tanks sent by Eastern European countries to Ukraine.

DESTROY TANKS

Ukraine's defence ministry said Russian forces were also pushing towards Sloviansk, which lies about 85 km (53 miles) to the west of Sievierodonetsk.

In Lysychansk, divided from Sievierodonetsk by a river, Russian forces fired on a bakery and several administrative and residential buildings, Governor Gaidai said on Monday. One civilian had been wounded, he said.

Some 60 km (40 miles) to the south, on the front line near Bakhmut, Ukrainian soldiers said the situation was difficult but they had no choice but to push back the Russians.

A unit commander who gave his name as Maxym appealed for more arms from Ukraine's allies.

"We need more anti-tank weapons. With more anti-tank weapons we would be able to destroy their tanks, to cause maximal damage and the enemy will be forced to flee from where they came," he told Reuters.

"This is our home, our land. We will fight for every piece of this land."

Russian forces were fortifying their positions in the Kharkiv region and shelling Ukrainian positions to keep hold of the territory they had occupied, Ukraine's military general staff said.

It said Russia was targeting civilian infrastructure in several towns and the regional administration said three civilians were killed and 10 wounded in shelling.

It was not possible to verify the toll. Moscow denies targeting civilians.

Russia's defence ministry said its forces had destroyed parts of an armoured vehicle repair facility in the Kharkiv region and killed more than 450 what it called "nationalists" in Horlivka and Kodema north of Donetsk. There was no word on the reported deaths from the Ukrainian side.

Inside Russia, the governor of the Kursk region, Roman Starovoit, said the village of Tyotkino near the border with Ukraine had come under fire from the Ukrainian side that targeted a bridge and some businesses on Monday morning. There were no immediate reports of casualties.

Russia calls its action in Ukraine a "special military operation" mounted to stamp out what it sees as threats to its own security. Ukraine and its Western allies dismiss this as nonsense and say it is an unprovoked war of aggression that risks turning into a wider European conflict.