Russia's despicable attacks against civilians in Irpin and Bucha are more evidence that Putin and his army are committing war crimes in Ukraine, Prime Minister of the UK Boris Johnson has said.

Russia's despicable attacks against innocent civilians in Irpin and Bucha are yet more evidence that Putin and his army are committing war crimes in Ukraine. "No denial or disinformation from the Kremlin can hide what we all know to be the truth – Putin is desperate, his invasion is failing, and Ukraine’s resolve has never been stronger," Johnson said on Twitter on Sunday.

The British prime minister assured that he would do everything in his power to exhaust the resources of the military machine of Russian President Vladimir Putin.

"I will do everything in my power to starve Putin's war machine. We are stepping up our sanctions and military support, as well as bolstering our humanitarian support package to help those in need on the ground," Johnson said.

He added that Deputy Prime Minister of the UK Dominic Raab has authorised additional financial support and the deployment of specialist investigators to Ukraine to support the International Criminal Court's investigation into atrocities committed by Russia in Ukraine.

"The UK has been at the forefront of supporting the International Criminal Court's investigation into atrocities committed in Ukraine, and Dominic Raab has authorised additional financial support and the deployment of specialist investigators – we will not rest until justice is served," Johnson said.