Russia has hit Ukraine's second-largest city, Kharkiv, with a massive drone and bomber attack, killing four people and injuring nearly 60, officials say.
Two people were also killed in Russian strikes on Kherson, in southern Ukraine, local authorities said.
Kharkiv Mayor Ihor Terekhov said 48 drones, two missiles and four glide bombs had been used against his city on Friday night, while more glide bombs were reportedly dropped on Saturday.
Earlier, Moscow said a massive wave of drone and missile attacks across Ukraine on Thursday night was in response to "terrorist attacks by the Kyiv regime", after attacks on Russian railway infrastructure and air bases last weekend.
In another development, Russian and Ukrainian officials released conflicting accounts about when a prisoner swap agreed at earlier talks would happen.
In Kharkiv, some 18 apartment buildings and 13 other homes were hit on Friday night, the mayor said. A baby and a 14-year-old girl were among the injured, he added.