Ukrainian troops are recapturing towns east of the capital Kyiv and Russian forces who had been trying to seize the city are falling back on their overextended supply lines, Britain said on Friday.

US President Joe Biden, meanwhile, was due to visit Poland for a first-hand look at the refugee crisis in which nearly a quarter of Ukraine's 44 million people have been uprooted and more than 3.6 million have fled to neighbouring states since the Russian invasion on Feb 24.

A month into their assault, Russian troops have failed to capture any major Ukrainian cities. An offensive that Western countries believe was aimed at swiftly toppling President Volodymyr Zelenskiy's government has been halted at the gates of Kyiv.

Battlelines there have...