Ukrainian president Volodymyr Zelensky says Russia now controls 20% of his country.
According to the leader, Russia controls Ukranian territory ‘much greater’ than the Netherlands, Belgium and Luxembourg combined.
His comments come as Russia's war on Ukraine enters its 100th day on Friday, June 3
Vladimir Putin's troops have set their sights on capturing eastern Ukraine since being repelled from around the capital Kyiv after their invasion began on 24 February.
While their advance has been much slower than Moscow expected, Russian troops have expanded their control beyond the 43,000 square kilometres (16,600 square miles) taken when Russia seized Crimea and parts of the Donbas in 2014.
"Today, about 20 per cent of our territory is under the control of the occupiers," Ukrainian President Volodymyr Zelensky said in an address to Luxembourg lawmakers on Thursday.
Russia's assault was killing up to 100 Ukrainian soldiers every day, Zelenskyy added.
Street fighting continues in the industrial hub of Severodonetsk in Lugansk, part of the Donbas. The strategic city is a key target for Moscow which already controls 80 per cent of the area, but Lugansk regional governor Sergiy Gaiday vowed Ukrainian forces would fight "until the end".
Valeriy Zaluzhnyi, the commander in chief of Ukraine's armed forces assessed that "the most difficult situation is in the Lugansk region, where the enemy is trying to displace our units".
He pleaded for modern armaments from NATO, telling France's top general, Thierry Burkhard that "the enemy has a decisive advantage in artillery."
"It will save the lives of our people".