Shells and rockets were landing at regular intervals in the industrial city of Severodonetsk in eastern Ukraine on Wednesday, AFP journalists saw.
One building was on fire and the few civilians seen only ventured out in intervals between the bombing, quickly running back for cover when it resumed.
Severodonetsk is the easternmost city held by Ukrainian forces on the eastern frontline.
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Russian forces have said they will focus their attacks in the south and east of the country, where they already hold large swathes of territory.
A UN humanitarian convoy of eight trucks reached the city on Tuesday, bringing food rations, flour, plastic sheeting and blankets for some 17,000 people, as well as four hospital electricity generators.
“Eastern Ukraine continues to bear the brunt of the intensifying hostilities, with thousands of people cut off from gas and water supplies and residential buildings repeatedly hit by shelling in Severodonetsk,” the UN humanitarian agency OCHA said.
One person was killed and five injured during shelling in the nearby town of Rubizhne on Tuesday and seven more “extricated themselves from the rubble,” the local governor Sergiy Gaiday said on social media.