Russian forces have destroyed the last bridge linking the eastern Ukrainian city of Sievierodonetsk to a Ukrainian held city on the other side of the river, cutting off all routes of evacuation for those remaining in the city, a Ukrainian official said on Monday evening.
Sergei Gaidai, the governor of Lugansk, said on social media that some 70% of Sievierodonetsk was now under Russian control, describing the situation for Ukrainian soldiers holding out in the city as "difficult, but under control".
At the same time, the destruction of the last bridge across the river to the twin city of Lysychansk meant that it was impossible to deliver humanitarian supplies, he said, nor remove any civilians still in Sievierodonetsk.
Russian artillery also pounded the Azot chemical plant on Monday, where, according to Gaidai, hundreds of civilians were sheltering.
Urgent calls for help
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.
President Volodymyr Zelenskyy said on Monday evening that the battle for Donbas would go down as one of the most brutal in European history.
"For us, the price of this battle is very high," he said, adding: "We draw the attention of our partners daily to the fact that only a sufficient number of modern artillery for Ukraine will ensure our advantage."
Ukraine needs 1,000 howitzers, 500 tanks and 1,000 drones among other heavy weapons, Presidential Adviser Mykhailo Podolyak said on Monday.
On Monday Russia's defence ministry said high-precision air-based missiles had struck near the railway station in Udachne northwest of Donetsk, hitting equipment that had been delivered to Ukrainian forces.
Russia's RIA news agency quoted a pro-Moscow separatist spokesperson Eduard Basurin as saying Ukrainian troops were effectively cut off in Sievierodonetsk and should surrender or die.
The situation risked becoming like Mariupol, "with a large pocket of Ukrainian defenders cut off from the rest of the Ukrainian troops", according to Damien Magrou, spokesperson for the International Legion for the Defence of Ukraine that has had forces in Sievierodonetsk.
During the fall of Mariupol last month, 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 neighbour.