Russian forces tightened their grip on the eastern Ukrainian city of Sievierodonetsk on Monday, a Ukrainian official said, cutting off the last routes for evacuating citizens.
Amid heavy bombardment, regional governor Sergei Gaidai said on social media that all bridges out of the city had been destroyed, making it impossible to bring in humanitarian cargoes or evacuate citizens.
"It is now fully impossible unfortunately to drive into the city, to deliver something to the city. Evacuation is impossible," Gaidai said.
He said 70 percent of the small industrial city – now the focus of one of the bloodiest battles of the war – was under Russian control, but that the remaining Ukrainian defenders were not completely blockaded.
"They have the ability to send the wounded to hospitals, so there is still access," he told Radio Free Europe/Radio Liberty's Ukrainian service. "It's hard to deliver weapons or reserves. Difficult, but not impossible."
Ukraine has issued increasingly urgent calls for more Western heavy weapons to help defend Sievierodonetsk, which Kyiv says could hold the key to the battle for the eastern Donbas region and the course of the war, now in its fourth month.
Ukraine's military command said in a briefing note that Russian forces were trying to take full control of Sievierodonetsk, but that an assault on Ukrainian positions in the southeast of the city had failed.
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"The battles are so fierce that fighting for not just a street but for a single high-rise building can last for days," Gaidai said earlier. He is governor of the Luhansk region that includes Sievierodonetsk.
Russian artillery fire pummeled the Azot chemical plant, where hundreds of civilians were sheltering, he said.
Damien Magrou, spokesperson for the International Legion for the Defense of Ukraine that has had forces in Sievierodonetsk, said the situation there risked becoming like Mariupol, "with a large pocket of Ukrainian defenders cut off from the rest of the Ukrainian troops".
"This is one of the reasons why it is so important that our Western partners deliver long range artillery as fast as possible," he said.
Russia's RIA news agency quoted a pro-Moscow separatist spokesperson, Eduard Basurin, as saying Ukrainian troops were effectively blockaded in Sievierodonetsk and should surrender or die.
Ukraine's account of civilians trapped in an industrial plant echoed the fall of Mariupol last month, where hundreds of civilians and badly wounded Ukrainian soldiers were trapped for weeks in the Azovstal steelworks.
Russia has denied targeting civilians in what it calls a "special operation" to restore Russian security and "denazify" its neighbor. Ukraine and its Western allies call this a baseless pretext for an invasion which has killed thousands of civilians and raised fears of wider conflict in Europe.
More than 5 million people have fled the assault and millions more are threatened by a global energy and food crisis due to disrupted gas, oil and grain supplies from Russia and Ukraine.