Ukrainian President Volodymyr Zelensky on Monday said Russia's large-scale offensive in the eastern Donbas region had begun, reports AFP.
"We can now confirm that Russian troops have begun the battle for the Donbas, which they have been preparing for a long time. A large part of the Russian army is now dedicated to this offensive," he said on Telegram.
"No matter how many Russian soldiers are brought here, we will fight. We will defend ourselves."
Fighting has intensified in eastern Ukraine after Russia withdrew troops from the region around the capital Kyiv and refocused its efforts on the Donbas region that pro-Moscow separatists have partly controlled since 2014.
Shortly before Zelensky's address, the regional governor of the eastern Lugansk region Sergiy Gaiday also announced the beginning of Russia's much-anticipated attack.
"It's hell. The offensive has begun, the one we've been talking about for weeks. There's constant fighting in Rubizhne and Popasna, fighting in other peaceful cities," he said on Facebook.
Russian shelling killed at least eight civilians in eastern Ukraine on Monday, according to local authorities.
Gaiday said four people died as they tried to flee the city of Kreminna in Lugansk, which Russian forces captured on Monday.
"Kreminna is unfortunately under the control of the orcs," he said, using a pejorative term to refer to Russian troops.
But Ukrainian presidential advisor Oleksiy Arestovich said Russian forces had not conquered Kreminna.
"Intense street fighting is unfolding there," he was quoted as saying by the television channel Ukraina 24.
In the neighbouring region of Donetsk, regional governor Pavlo Kyrylenko said four other civilians died after Russian bombardment.
A large Russian offensive in the Donbas region had been predicted by Ukraine's army for weeks.
Russian President Vladimir Putin said he launched the military operation to save the region's Russian-speaking population from a "genocide" carried out by a "neo-Nazi" Kyiv regime.
Putin recognised the independence of two self-proclaimed separatist republics in Donetsk and Lugansk shortly before the full-scale Russian invasion began on February 24.
