Russia intends to take Ukraine in its entirety but the Russian army failed to deliver on the first day of its invasion, British Defense Secretary Ben Wallace said on Friday.

Russia launched its invasion by land, air and sea on Thursday following a declaration of war by President Vladimir Putin, in the biggest attack on a European state since World War II.

Missiles pounded the Ukrainian capital on Friday as Russian forces pressed their advance and Ukrainian President Volodymyr Zelenskyy pleaded with the international community to do more, saying sanctions announced so far were not enough.

"It's definitely our view that the Russians intend to invade the whole of Ukraine," Wallace told Sky.

Putin says Russia is carrying out "a special military operation" to stop the Ukrainian government from committing genocide against its own people – an accusation the West calls baseless. He also says Ukraine is an illegitimate state whose lands historically belong to Russia.

Wallace said the Russian army had failed to deliver its key objectives, directly contradicting the Russian Defense Ministry which said it had achieved all of its main aims on the first day of the military operation.

"Contrary to great Russian claims, and indeed President Putin's sort of vision that somehow the Ukrainians would be liberated and would be flocking to his cause, he's got that completely wrong, and the Russian army has failed to deliver, on day one, its main objective," Wallace said.