On Tuesday, Ukrainian President Volodymyr Zelensky said that Ukraine’s fight against Russian troops in the eastern Donbas region would determine the course of the war and demanded that Ukraine remain strong in the face of a devastating Russian attack on two major cities.

With the outcome of the conflict up in the air, NATO chief Jens Stoltenberg backed Ukraine’s increasingly urgent call for more weapons, urging allies to speed up arms deliveries to Kyiv.

Russian troops have stepped up efforts to cut off Ukrainian troops remaining in the industrial hub of Severodoentsk, destroying all three bridges linking the river to the twin cities of Lysychansk.

The head of the city administration, Oleksandr Stryuk, told Ukrainian television that some 500 civilians were sheltering from “heavy fire” at the Azot chemical plant in Severodonetsk.

On Wednesday, Russia’s Defence Ministry said it was preparing to organise an evacuation from the plant to separatist-held areas in the Luhansk region.

According to regional governor Sergei Gaiday, Ukrainian troops have been pushed back from the centre of Severodonetsk, and the Russians, who control 70 to 80% of the city, are trying to surround it.

Occupying Severodonetsk would open the way for Slovyansk and another major city, Kramatorsk, and push Moscow to conquer the Donbas. This Russian-speaking region has existed since 2014 and is partly owned by pro- Separatist control of the Kremlin.