In its two-week assault on Severodonetsk, Russia has advanced to encircle two-thirds of the cavalry positions of the Ukrainian resistance.
In their current formations, Kyiv sources said that Ukrainian troops could hold out for several weeks.
Moscow forces have launched constant artillery attacks to pave the way for ground attacks.
Ukrainian officials have stressed that their troops would have a good chance of clinging to the territory if they were given missile systems to fire Russian cannons.
Serhiy Haidai, Luhansk regional governor, said the Russians were using “the same tactics over and over again”.
“They attack for several hours, three, four, five hours in a row and then attack,” he added.
“Those who attack die. Then the bombing and the attack continue again, and so on until they open up somewhere.”
In a ground attack, Frédéric Leclerc-Imhoff, 32, a journalist working for the French channel BFMTV, was killed while covering a humanitarian bus leaving the city.