With the city effectively cut off by Russian forces, Serhiy Haidai says delivering supplies and evacuating civilians are now impossible.
Fierce fighting is taking place in the eastern city where Ukrainian officials said Russian artillery had driven its forces out of the centre.
For weeks capturing Severodonetsk has been a top military goal for Russia.
Taking Severodonetsk and the nearby city of Lysychansk would give Moscow control of the entire Luhansk region, much of which is already controlled by Russian-backed separatists.
Halyna Pastushuk has this report.
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