The Russian defense ministry says its forces are in "full control" of Luhansk. It is one of Ukraine's two neighboring eastern regions Russian forces have been trying to seize.

The ministry said in a statement on Sunday that Minister Sergei Shoigu told President Vladimir Putin that their forces had taken "full control" of Luhansk. The ministry had earlier claimed the capture of Lysychansk, a city seen as Ukraine's last stronghold in the region.

The leader of pro-Russian militants in Luhansk, Leonid Pasechnik, declared on social media on Sunday that the day has been inscribed in history forever.

The General Staff of the Armed Forces of Ukraine announced on social media on Sunday that it decided to withdraw its soldiers from Lysychansk to save their lives.

It said that otherwise the situation would "lead to fatal consequences" as Russian forces are superior in artillery, ammunition and personnel.

Ukrainian President Volodymyr Zelenskyy said in a video address on Sunday that "if the command of our army withdraws people from certain points of the front where the enemy has the greatest fire superiority, in particular this applies to Lysychansk, it means only one thing: we will return thanks to our tactics, thanks to the increase in the supply of modern weapons."

The mayor of Slovyansk in Donetsk said in a social media video on Sunday that his city has experienced the fiercest offensive in the invasion, which resulted in many casualties.

Ukraine's public broadcaster quoted a Donetsk regional government spokesperson as saying the attack on Slovyansk left six people dead and 15 others wounded.

A senior pro-Russian militant said on social media that a battle has already begun in a town in Donetsk, about 30 kilometers west of Lysychansk.