Russia has intensified its offensive in the Donbas while its forces advance on the Luhansk front.
Ukraine s president Zelenskiy described the situation in Donbas as extremely difficult in his latest national address.
Sergiy Gaiday, the regional governor of Ukraine's eastern Luhansk region, said Russia is trying to destroy the city of Severodonetsk, with fighting on the outskirts of the city.
Gaiday said the frontline city is now at risk of encircling after 12 people were killed and another 40 wounded by Russian shelling.
Shelling continues from morning to night, and also throughout the night, he said in a video posted on the Telegram messaging app.
Severodonetsk and Lysychansk, the city on the other side of the Siverskiy Donets River, form the eastern part of a Ukrainian-held pocket Russia has been trying to overrun since mid-April after failing to capture Kyiv.
In the neighbouring Donetsk region, the governor Pavlo Kyrylenko said on Saturday that seven civilians had been killed and 10 wounded.
New networks of trenches and checkpoints have cropped up as the city prepares to defend against a new attack, according to a report from Kharkiv, just 50 km from the border with Russia.