The situation in Bakhmut, on Ukraine’s eastern frontline, is becoming “more and more difficult,” according to Ukraine’s President Volodymyr Zelensky.
For over six months, Russian forces have been attempting to take the city.
“The enemy is constantly destroying everything that can be used to defend our positions,” said Mr Zelensky.
During a visit to Kyiv on Monday, US Treasury Secretary Janet Yellen warned China against arming Russia.
Some of the fiercest fighting since Russia’s invasion of Ukraine a year ago has taken place in Bakhmut, in Ukraine’s Donetsk region, which is controlled by Russia and its proxy forces.
Russian forces’ efforts to capture the industrial city have recently intensified, with their troops gaining ground. The Russian state news agency RIA broadcast footage of Su-25 fighter jets roaring over Bakhmut.
Despite the Russian gains, a Reuters reporter who visited the area on Monday said there was no indication that Ukrainian forces were preparing to withdraw, and that reinforcements were on their way.
The separatist leader of the self-proclaimed Donetsk People’s Republic, Denis Pushilin, said “practically all roads” into the city were “under [Russian] fire control”.
And the commander of Ukraine’s ground forces, Col Gen Oleksandr Syrskyi, said the situation around Bakhmut was “extremely tense”.