Russia on Tuesday faced increasing isolation over its invasion of Ukraine, with fierce resistance on the ground denying President Vladimir Putin decisive early gains despite heavy shelling and a huge military convoy outside the capital, Kyiv.

Ukrainian officials reported a Russian bombardment of Kharkiv, the country's second largest city, had killed dozens of civilians. It was not possible to independently verify the casualty figures.

"Barbaric rocket attacks and MLRS (multiple launch rocket systems) of peaceful cities are evidence that they are no longer able to fight armed Ukrainians," Ukrainian Defense Minister Oleksii Reznikov said on Facebook.