Russia said Tuesday it would establish a humanitarian corridor to evacuate civilians from a chemical plant in Severodonetsk, as the two sides battled for control of the key city in Ukraine's eastern Donbas region.
Russian forces have stepped up efforts to cut off the Ukrainian troops still in the industrial hub, blowing up three bridges which connect it to Lysychansk on the other side of a river.
Ukrainian President Volodymyr Zelensky meanwhile once again appealed for heavy weapons from the West, criticising the "restrained behaviour" of some European leaders.
Moscow has for week targeted the twin cities as the last areas in the Lugansk region of the Donbas still under Ukrainian control.
Severodonetsk was not isolated, the head of the city's administration, Oleksandr Stryuk, told Ukrainian television, but communication was "complicated" with the situation on the ground changing every hour.
Around 500 civilians were taking shelter under "heavy fire" in the Azot chemical plant in Severodonetsk, Stryuk said.
The Russian army said it would establish a humanitarian corridor to evacuate civilians from the plant to the separatist-controlled Lugansk region on Wednesday.
"Remaining civilians in Severodonetsk are almost entirely cut off from aid supplies after the destruction of the last bridge into the city," Jan Egeland, secretary general of the Norwegian Refugee Council said in a statement.
It was impossible to "overstate the seriousness of the current situation for civilians trapped in Severodonetsk", he said, calling on "all parties... to allow safe passage for civilians".
- 'Surrender or die' -
Lugansk regional governor Sergiy Gaiday said Monday Ukraine's forces had been pushed back from Severodonetsk's centre with the Russians controlling 70 to 80 percent of the city in their attempt to "encircle it".
With Russia turning the screw on the city, Ukrainian forces have two choices: "to surrender or die", said Eduard Basurin, a representative for pro-Russian separatists.
Capturing Severodonetsk would open the road to Sloviansk and another major city, Kramatorsk, in Moscow's push to conquer Donbas, a mainly Russian-speaking region partly held by pro-Kremlin separatists since 2014.
Zelenksy, in comments to Danish journalists Tuesday, insisted that the war could only end once Ukrainians were the only ones left on its territory.
How long that took depended "very much" on international support, and "the personalities of the leaders of European states".
He regretted what he called, "the restrained behaviour of some leaders" which, he said, had "slowed down arms supplies very much".
Zelensky has repeatedly urged the west to deliver heavy weapons to Ukraine as quickly as possible.
- 'Tear off their arms' -
From an elevated position in Lysychansk, an AFP team saw black smoke rising from the Azot factory in Severodonetsk and another area in the city.
Lysychansk itself has massive damage after months of shelling, with no water, electricity or phone signal.
The Ukrainian military is using high ground in the city to exchange fire with Russian forces fighting for control of Severodonetsk, just across the water.
Lysychansk resident Maksym Katerin buried his mother and stepfather in his garden on Monday after a shell ripped through his yard, killing them instantly.
"I don't know who did this, but if I knew, I would tear off their arms," he said.
Katerin's mother was lying on the ground, "her stomach was ripped and her guts were falling out. She was a very good, kind and helpful woman. Why did they do this to her?" Panicheva said.
"They bomb and they bomb, and we don't know what to do."
In the eastern town of Novodruzhesk Tuesday, there was still a smell of burning and smoke from a group of houses destroyed by shelling.
"It's not safe anywhere," said a soldier standing at the local fire station. "There are tons of people (still) here."
- 'Positive signal' -
The European Union needs to "give a positive signal" to Ukraine and be "open" to granting it candidate status, France's Europe minister, Clement Beaune, said Tuesday.
Ukraine has applied to become a member of the bloc, with the European Commission due to give its recommendation in the coming days. But some member states are sceptical about potentially fast-tracking Ukraine's accession.
The process would "take time", Beaune said, adding that the first priority was to "stop the war".
Russian energy giant Gazprom said Tuesday it would reduce gas deliveries to the EU via the Nord Stream pipeline by 40 percent, due to the delayed return of compressor units from German company Siemens.
A number of European countries, including Germany, where the underwater pipeline makes land, are highly reliant on supplies of Russian gas for their energy needs.
"The Kremlin has used our dependency on Russian fossil fuels to blackmail us," European Commission chief Ursula von der Leyen said on a visit to Israel, where the EU hopes to strengthen its energy ties.
The Kremlin meanwhile said it had not received a request from London to intervene in the case of two Britons sentenced to death by pro-Moscow separatist authorities in eastern Ukraine.
Aiden Aslin and Shaun Pinner, along with Moroccan Saaudun Brahim, were convicted of acting as mercenaries for Ukraine by the self-proclaimed Donetsk People's Republic.
"Everything will depend on the appeal from London, and I am sure that the Russian side will be ready to consider it," Kremlin spokesman Dmitry Peskov told reporters.
Russia also announced it was blacklisting 49 UK citizens, including defence officials and prominent journalists from the BBC, The Financial Times and The Guardian.