Russia on Sunday attacked Ukraine in one of the largest aerial assaults of the war, signaling a new wave of escalation as it used a rarely launched hypersonic ballistic missile.

The use of the Oreshnik missile, which Russia has used against Ukraine only twice before, came after the Kremlin accused Kyiv of striking a college dormitory, killing 21 people, and vowed retaliation.

Russia had halted attacks earlier this month as part of a brief US-brokered ceasefire, but broader peace talks are frozen as the two sides remain deadlocked on the battlefield and Ukraine uses drones to strike deeper into Russian territory.