Ukrainian President Volodymyr Zelenskyy accused Russia of trying to "destroy the Donbas" as the country braced itself for a large scale offensive in the east.
"Russian soldiers are preparing for an offensive in the east of our country in the near future. They literally want to finish off and destroy the Donbas," Zelenskyy said in a video message.
"Just as the Russian military is destroying Mariupol, they want to destroy other cities and other communities in the Donetsk and Luhansk regions", he continued, adding that officials would do "everything" to defend the area.
Meanwhile, the southeastern port city of Mariupol, which has been subjected to constant shelling since early on in the war, was still holding out as Russia demanded that troops there surrender or die.
Russia's defence ministry said that "all those who have given up their arms will be guaranteed to have their lives saved."
Ukrainian foreign minister Dmytro Kuleba told CBS on Sunday that Russian troops had decided "to raze the city (of Mariupol) to the ground at any cost."
Other officials said that Ukrainian soldiers in Mariupol would stay and fight in the city "to the end".
Zelenskyy once again on Sunday called for further sanctions on Russia, including against their energy sector.
“Everyone in Europe and America already sees Russia openly using energy to destabilize Western societies,” he said.
“All of this requires greater speed from Western countries in preparing a new, powerful package of sanctions.”