Russian forces now occupy about one-fifth of Ukrainian territory, President Volodymyr Zelensky has said, as the battle clocked 100 days since the start of the invasion.

Mr Zelensky pleaded for more Western arms to help reach a battlefield “inflection point” and prevail in the war as Russia tightened its grip on a key target in the eastern Donbas region.

Mr Zelensky told Luxembourg’s parliament via videolink battle lines now stretched more than 1,000 km.

Russian forces, backed by heavy artillery, control most of Sievierodonetsk — now largely in ruins — after days of fierce fighting in which they have taken losses, Britain’s defence ministry said in its daily intelligence report.

“The enemy is conducting assault operations in the settlement of Sievierodonetsk,” Ukraine’s armed forces general staff said, adding that Russian forces were also attacking other parts of the east and northeast.

At least four civilians were killed and 10 wounded in the east and northeast, other officials said.

Russia denies targeting civilians.

If Russia fully captures Sievierodonetsk and its smaller twin Lysychansk on the west bank of the Siverskyi Donets river, it would hold all of Luhansk, one of two provinces — with Donetsk — in the Donbas that Moscow claims on behalf of separatists.

Capturing Luhansk would fulfil one of Russian President Vladimir Putin’s stated aims and solidify a shift in battlefield momentum after his forces were pushed back from the capital Kyiv and from northern Ukraine.

A Ukrainian main battle tank in Severodonetsk, eastern Ukraine. Photo: Getty

The war is having a massive impact on the world economy. Russia has captured some of Ukraine’s biggest seaports and its navy controls major transport routes in the Black Sea, blocking Ukrainian shipments and deepening a global food crisis.

Russia and Ukraine together account for nearly one third of global wheat supplies, while Russia is also a key fertiliser exporter and Ukraine a major supplier of corn and sunflower oil.

Ukraine’s foreign ministry spokesman Oleg Nikolenko said Kyiv was working with international partners to create a UN-backed mission to restore Black Sea shipping routes and allow the export of Ukrainian farm produce.

Moscow criticised as “self-destructive” a decision by the European Union this week to cut 90 per cent of oil imports from Russia by the end of 2022, saying the move could destabilise global energy markets.

Vladimir Putin meets families awarded Orders of Parental Glory. Photo: Getty

But Russian President Vladimir Putin appears intent on conveying the impression of business as usual as the Ukraine war continues.

As his army fought its way into the Ukrainian city of Sievierodonetsk this week, Mr Putin was making awkward small talk in a televised ceremony to honour parents of exceptionally large families.

Since the start of May, he has met — mostly online — with educators, oil and transport bosses, officials responsible for tackling forest fires, and the heads of at least a dozen Russian regions, many of them thousands of miles from Ukraine.

Along with several sessions of his Security Council and a series of calls with foreign leaders, he found time for a video address to players, trainers and spectators of the All-Russian Night Hockey League.

The appearance of solid, even boring routine is consistent with the Kremlin’s narrative that it is not fighting a war — merely waging a “special military operation” to bring a troublesome neighbour to heel.

For a man whose army has heavily underperformed in Ukraine and been beaten back from its two biggest cities, suffering untold thousands of casualties, Mr Putin shows no visible sign of stress.

But as the war grinds on with no end in sight, Mr Putin faces an increasing challenge to maintain the semblance of normality.

Economically, the situation will worsen as sanctions bite harder and Russia heads towards recession.

Militarily, Putin’s forces have gradually advanced in eastern Ukraine but the United States and its allies are stepping up arms supplies to Kyiv, including a US promise this week of advanced rocket systems.

Should Russia’s offensive falter, Mr Putin could be forced into declaring a full-scale mobilisation of reserves to bolster his depleted forces, Western defence experts say.

Divisions are emerging between Ukraine’s most hawkish backers — the United States, Britain, Poland and the Baltic states — and a group of countries including Italy, France and Germany which are pressing to bring an end to the war.