Ukrainian President Volodymyr Zelensky vowed victory on the 100th day of Russia's invasion today, even as Russian troops pounded the eastern Donbas region.

However, Ukraine said it recaptured a large chunk of territory in fierce fighting for Sievierodonetsk and foiled an attempt by Russian troops to advance from the devastated eastern industrial city.

Thousands of people have been killed and millions sent fleeing and towns turned into rubble, since Russian President Vladimir Putin ordered his troops into Ukraine on 24 February.

"Victory will be ours," Mr Zelensky said in a video address similar to one he posted at the onset of the war outside government buildings in Kyiv.

But Kremlin spokesman Dmitry Peskov said: "certain results have been achieved", pointing to the "liberation" of some areas from what he called the "pro-Nazi armed forces of Ukraine".

Bomb disposal experts make a controlled explosion of unexploded missiles, artillery shells and mines they have retrieved during the last week in the Borodianka area of Ukraine

It comes as a French volunteer fighter in Ukraine was confirmed dead after being caught in artillery fire in the Kharkiv region.

Meanwhile France's President Emmanuel Macron said his Russian counterpart Vladimir Putin had committed a "historic and fundamental error" by invading Ukraine and was now "isolated".

"I think, and I told him, that he made a historic and fundamental error for his people, for himself and for history," he said in an interview with French regional media.

The West has sent ever more potent weapons to Ukraine and piled on ever more stringent sanctions, with the EU also today formally adopting a ban on most Russian oil imports.

Mr Putin's alleged girlfriend, former gymnast Alina Kabaeva, was also added to an assets freeze and visa-ban blacklist, along with Russian army personnel suspected of war crimes.

A photograph shows graves in a residential area of Mariupol today

At the same time, the United Nations said it was leading intense negotiations with Russia to allow tens of millions of tons of grain to leave Ukrainian ports to avert a global food crisis.

"I am optimistic that something could give in, something could be made," said Amin Awad, the UN crisis coordinator for Ukraine, voicing hope that we could "see a breakthrough".

Russian troops now occupy a fifth of Ukraine's territory and Moscow has imposed a blockade on the country's Black Sea ports.

The UN has warned that especially African countries, which imported more than half of their wheat consumption from Ukraine and Russia, face an "unprecedented" crisis caused by the conflict.

Food prices in Africa have already exceeded those in the aftermath of the 2011 Arab springs and the 2008 food riots.

This school was destroyed as a result of Russian shelling in Kharkiv, Ukraine

President Putin today met the head of the African Union, Senegalese President Macky Sall, at his Black Sea residence in Sochi.

At the opening of those talks, Mr Sall told Putin to "become aware" African countries "are victims" in the Ukraine conflict.

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Mr Putin's troops are now concentrating their forces in the Donbas, in the east, where some of the fiercest fighting is centred on the industrial hub city of Severodonetsk.

Fighting continues in Severodonetsk's city centre, the president's office said, adding that the invaders were "shelling civilian infrastructure and Ukrainian military".

Severodonetsk "is the toughest area at the moment," Mr Zelensky said last night.

"For 100 days, they have been levelling everything", Lugansk regional governor Sergiy Gaiday said on Telegram.

Accusing Russian troops of destroying hospitals, schools and roads, Mr Gaiday said, however, that "we are only getting stronger.

"Hatred of the enemy and faith in our victory make us unbreakable."

Bomb disposal experts at work in Borodianka, Ukraine

Ukrainian troops were still holding an industrial zone, he added, a situation reminiscent of Mariupol, where a steelworks was the south-eastern port city's last holdout until Ukrainian troops finally surrendered in late May.

The situation in Lysychansk - Severodonetsk's twin city, which sits just across a river - also looked increasingly dire.

About 60% of infrastructure and housing had been destroyed, while internet, mobile network and gas services had been knocked out, said the city's mayor Oleksandr Zaika.

"The shelling is getting stronger every day," he said.

In the city of Sloviansk, about 80 kilometres from Severodonetsk, the mayor has urged residents to evacuate as bombing intensified and water and electricity are cut off.

Student Gulnara Evgaripova, 18, recounted heavy bombardments as she boarded a minibus to leave the city.

"The situation is getting worse, the explosions are stronger and stronger, and the bombs are falling more often," she told AFP.

Ekaterina Perednenko, a paramedic, said: "I am scared that there will be nothing to come back to".
In a statement, Awad said: "This war has and will have no winner.

"Rather, we have witnessed for 100 days what is lost: lives, homes, jobs and prospects."

Children playing today in the Kyiv suburb of Borodianka in Ukraine

The United Nations said today there would be no victor from Russia's invasion.

"This war has and will have no winner. Rather, we have witnessed for 100 days what is lost: lives, homes, jobs and prospects," Amin Awad, Assistant Secretary-General and United Nations Crisis Coordinator for Ukraine, said in a statement.

With one-fifth of Ukraine under occupation, President Volodymyr Zelensky yesterday told Western officials in Bratislava that the war faced an "inflection point" depending on whether the West could provide the weapons to subvert the huge advantage in equipment and troops Russia has in the east.

Some feel the West has already missed its best chance.

"My sense is that the West made a big mistake. Six weeks ago, when the Russians were in retreat ... That's when the Americans should have given Ukrainians HIMARS," said Jamie Shea.

He is a former senior NATO official now at the Friends of Europe think-tank in Brussels, referring to the advanced rocket systems being promised by the United States.

After over-stretching their supply lines in the early weeks of the war, the Russians were forced to withdraw from positions around the capital Kyiv and other northern regions.

But in recent weeks they have put Ukraine on the back foot in eastern Ukraine by concentrating overwhelming fire power on a relatively small front.