KYIV-  Russia told Ukrainian forces holed up in a chemical plant in the embattled city of Sievierodonetsk to lay down their arms by early Wednesday, pressing its advantage in the battle for control of eastern Ukraine.

Ukraine is calling for an increase in Western heavy weapons after Russia committed the bulk of its firepower to the eastern Donbas region, a topic expected to feature prominently at a meeting of NATO defence ministers on Wednesday in Brussels.

Ukraine says more than 500 civilians are trapped alongside soldiers inside the Azot chemical factory where its forces have resisted weeks of Russian bombardment and assaults that have reduced much of Sievierodonetsk to ruins.

Fighters should “stop their senseless resistance and lay down arms” from 8 a.m. Moscow time (0500 GMT),” ​Mikhail Mizintsev, head of Russia’s National Defence Management Centre told the Interfax news agency.

Civilians would be let out through a humanitarian corridor, Mizintsev said. The Azot bombardment echoes the earlier siege of the Azovstal steelworks in the southern port of Mariupol, where hundreds of fighters and civilians took shelter from Russian shelling.

Those inside surrendered in mid-May and were taken into Russian custody. Shelling on Azot was so heavy that “people can no longer stand it in the shelters, their psychological state is on edge,” said regional governor Serhiy Gaidai of Luhansk, one of two eastern provinces Moscow claims on behalf of separatist proxies.

The Russian assault on Luhansk’s Sievierodonetsk – a city of barely more than 100,000 people before the war – is currently the focal point of what has been called the battle of the Donbas. Kyiv has said 100-200 of its soldiers are killed each day, with hundreds more wounded.

Ukraine is still trying to evacuate civilians from Sievierodonetsk after Russian forces destroyed the last bridge across a river to the Ukrainian-held twin city of Lysychansk. Russian forces have shelled Lysychansk, which lies on higher ground on the western bank of the Siverskyi Donets river.

Ground has changed hands several times over the past few weeks, and Ukrainian officials have given little indication they will back down. But with all the bridges leading from Sievierodonetsk now destroyed, Ukrainian forces risk being encircled.

“We have to hold strong … The more losses the enemy suffers, (the) less strength it will have to pursue its aggression,” Zelenskiy said in an address late Tuesday.

‘UNABLE TO LEAVE’ Russia gives no regular figures of its own losses but Western countries say they have been massive as President Vladimir Putin seeks to force Kyiv to cede full control of two provinces, Luhansk and Donetsk, collectively known as the Donbas.

Momentum in Sievierodonetsk has shifted several times over the past few weeks – with Russia concentrating its overwhelming artillery firepower on urban districts