Russian troops have sharply stepped up their attacks in eastern Ukraine, Kyiv's military said on Sunday, as a NATO official predicted Moscow would increase the pace and intensity of its assaults with talks to end the war approaching.

Russia launched ballistic missiles and more than 100 drones in a wave of attacks across Ukraine overnight that killed three people and injured at least 16, including a child, authorities said.

Officials say Russian forces have targeted Ukraine’s energy and gas infrastructure in a “massive” nighttime missile attack, while Ukrainian drones struck an important oil refinery inside Russia.