Russia's attacks on Ukraine's energy sector on Monday night - as temperatures dropped to -20C (-4F) - were "barbaric" and "particularly depraved", UK Prime Minister Sir Keir Starmer has said, BBC reported. 

He made the comments after speaking to US President Donald Trump hours after Russia hit power plants and critical infrastructure in the capital, Kyiv, and elsewhere.

The attacks came at the end of a week-long pause that Trump had asked Russia's President Vladimir Putin to observe as a fierce cold swept Ukraine, according to BBC.