Ukraine is bracing for a battle for the control of its industrial east, appealing to people to immediately evacuate from the Donbass region before Russia intensifies its offensive there.
Ukraine is trying to evacuate as many trapped civilians as possible as Russian forces pound cities and towns in the east and south of the country.
Deputy Prime Minister Irena Vereshchuk announced on Thursday an agreement with Russia on opening 10 safe corridors, mostly in southern and eastern Ukraine.
Vereshchuk said residents trying to leave the besieged city of Mariupol would have to use their own vehicles.
Ukrainian officials say Russia has been regrouping for a new offensive in the east and south, and want civilians to leave those areas while they still can.
"Evacuate! The chances of saving yourself and your family from Russian death are dwindling every day," said Sergiy Gaidai, the governor of the Luhansk region.
Gaidai added that Russian troops had not made any significant breakthroughs.
"These few days may be the last chance to leave," Gaiday wrote to residents on Facebook, cautioning that Russian forces were "trying to cut off all possible ways of taking people out".
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Local officials reported heavy Russian shelling and rocket fire in the southern region of Kherson in the last few days.
Ukrainian Presidential adviser Oleksiy Arestovycvh said Russian air attacks were now focused mainly on areas of eastern Ukraine.
He said he believed Russian efforts to surround Ukrainian troops in the east would be in vain, adding: "The situation is under control."
Ukraine's military says Russia wants to entrench a land passage between two separatist, self-proclaimed people's republics in Donbass in east and the southern region of Crimea that Russia seized and annexed in 2014.
Oleh Synyehubov, governor of the eastern Kharkiv region, said civilian areas had been shelled 48 times in the past 24 hours to "put pressure on the civilian population of Kharkiv and destroy civilian infrastructure".
He said three civilians had been killed and many homes destroyed in shelling of Balakliya, a town close to the occupied city of Izyum, from where Ukraine says it can no longer evacuate civilians.
Presidential adviser Arestovycvh said the besieged city of Mariupol, which has been under siege for most of the Moscow's military operation, was holding out.
At least 160,000 civilians are trapped without power and with little food or running water, according to Mayor Vadym Boychenko, who puts the civilian death toll in the city at about 5,000.
Multiple attempts to agree safe passage for buses to take supplies to Mariupol and bring out civilians have failed since Russia attacked Ukraine on February 24, with each side blaming the other.