Ukraine has said it had recaptured a swathe of the battlefield city of Sievierodonetsk, in a rare counter-offensive against Russia's main assault force that had been steadily advancing in the east.

The Ukrainian claim could not be independently verified and Moscow said its own forces were making gains there. But it was the first time Kyiv has claimed to have launched a big counter-attack in Sieverodonetsk after days of yielding ground there.

Russia has concentrated its forces on Sievierodonetsk in recent weeks for one of the biggest ground battles of the war, with Moscow appearing to bet its campaign on capturing one of two eastern provinces it claims on behalf of separatist proxies.

Both sides have claimed to have inflicted huge casualties in the fighting for the small industrial city, a battle that military experts say could determine which side has the momentum for a prolonged war of attrition in coming months.

Residents stand amid the rubble of their home in Sloviansk in the Donbas region

In the diplomatic sphere, Kyiv rebuked French President Emmanuel Macron for saying it was important not to "humiliate" Moscow.

"We must not humiliate Russia so that the day when the fighting stops we can build an exit ramp through diplomatic means," Mr Macron said in an interview with regional newspapers published today, adding he was "convinced that it is France's role to be a mediating power".

Ukrainian Foreign Minister Dmytro Kuleba tweeted in response: "Calls to avoid humiliation of Russia can only humiliate France and every other country that would call for it.

"Because it is Russia that humiliates itself. We all better focus on how to put Russia in its place. This will bring peace and save lives."

Ukraine now says its aim is to push Russian forces back as far as possible on the battlefield, counting on advanced missile systems pledged in recent days by the United States and Britain to swing the war in their favour.

Asked about Mr Macron's mediation offer, Ukrainian presidential adviser Mykhailo Podolyak said: "Until we receive weapons in their full amount, until we strengthen our positions, until we push them [Russia's forces] back as far as possible to the borders of Ukraine, there is no point in holding negotiations."

Moscow has said the Western weapons will pour "fuel on the fire," but will not change the course of what it calls a "special military operation" to disarm Ukraine and rid it of nationalists.

Members of the public in the Sumy region walk past a destroyed building

Serhiy Gaidai, the Ukrainian governor of Luhansk province which includes Sievierodonetsk, said overnight that Ukrainian forces previously in control of just 30% of the city had mounted a counter-attack, recapturing another 20% of it.

Russia's defence ministry said its troops were forcing the Ukrainians to withdraw across the Siverskiy Donets river to Lysychansk on the opposite bank.

Mr Gaidai said the Russians were blowing up bridges across the river to prevent Ukraine bringing in military reinforcements and delivering aid to civilians in Sievierodonetsk.

"Right now, our soldiers have pushed them back, they [the Russians] are suffering huge casualties," Mr Gaidai said in a live TV broadcast.

"The Russian army, as we understand, is throwing all its efforts, all its reserves in that direction."

Read more: Latest Ukraine stories

Tens of thousands are believed to have died, millions have been uprooted from their homes and the global economy disrupted in a war that marked its 100th day yesterday.

The war has had a devastating impact on the global economy, especially for poor food-importing countries.

Ukraine is one of the world's leading sources of grain and cooking oil, but those supplies were largely cut off by Russia's closure of its Black Sea ports, with more than 20 million tonnes of grain stuck in silos.

An armoured vehicle is towed on a motorway near the city of Soledar in the Donbas region

Ukraine blames Russia for blaze at Orthodox church

A wooden Orthodox church on one of Ukraine's most sacred sites was set ablaze amid fierce fighting in the Donbas.

"As a result of hostilities, a large-scale fire broke out on the territory of the All Saints Skete of the Holy Dormition Sviatogirsk Lavra," a statement said.

"The flames completely engulfed the main church of the monastery," it added.

Ukrainian culture minister Oleksandr Tkachenko blamed Russian forces for the blaze, adding that about 300 displaced Ukrainians had been seeking shelter there, including 60 children.

Russia's defence ministry said in a statement that its military was not conducting operations in the region.

The area hosts one of the largest wooden churches in Ukraine and it was reportedly caught in the fighting several times already in the last month. Before the war, the holy site drew thousands of pilgrims a year.