Ukraine’s President Volodymyr Zelensky says that Russian forces have seized 20% of his country’s territory, as Moscow’s invasion nears its 100th day.
Addressing lawmakers in Luxembourg, he added that the front line extended for more than 1,000km (621 miles).
“All combat-ready Russian military formations are involved in this aggression,” he told MPs via videolink.
Russian forces have been intensifying attacks on the city of Severodonetsk in the eastern Donbas region.
UK defence officials say Russia has seized most of the city and are making “steady local gains, enabled by a heavy concentration of artillery”.
Severodonetsk is the easternmost city under Ukrainian control and regional governor Serhiy Haidai said Russia was trying to break through defences in the city “from all directions”.
However he said Ukrainian troops were carrying out counter-attacks, “pushing back the enemy on some streets and taking several prisoners”.
Intense street-to-street fighting in the city had hampered evacuations, he said, describing such efforts as “extremely dangerous”.
In a video address late on Thursday evening, Mr Zelensky said the situation in Donbas had not changed significantly that day but that Ukrainians had experienced “some success” in battles in Severodonetsk.
Some 15,000 civilians remain trapped in the city, with many of them taking shelter at the massive Azot chemical plant.