STORY: Ukrainian servicemen fired a tank in the direction of the Russian troops.
Positioned in the industrial part of the city, a serviceman was seen giving an instruction to a tank crew to open fire, followed by a tank firing multiple times.
Russian and Ukraine forces have been fighting for weeks for control of Sievierodonetsk.
Reuters video showed a group of three servicemen, one wearing flak jacket over a sleeveless shirt, taking cover in a dusty basement, as the Russian forces responded and pounded the area with heavy shelling.
Ukrainian troops are reportedly still holding out at a chemical plant in the east bank city of Sievierodonetsk.
Zelenskiy said late on Tuesday (June 21) the military situation in Luhansk region was very difficult, and his advisor Oleskiy Arestovych said Russian forces could cut off Sievierodonetsk from Ukrainian-held territory.