The attack on the capital occurred ahead of expected ceasefire negotiations in Saudi Arabia in which Ukraine and Russia are expected to hold indirect U.S.-mediated talks.

Russian forces launched a massive drone attack overnight on Ukraine's Kharkiv region, injuring 21 people and damaging residential buildings and storage facilities, emergency services and officials said on Thursday.

The U.S. reached deals with Ukraine and Russia to pause their attacks over the Black Sea and against each other's energy targets, but it was not clear when and how the deals would come into force.