Russian forces bombarded scores of towns in Ukraine on Christmas Day as Russian President Vladimir Putin said he was open to negotiations, a stance Washington has dismissed as posturing because of continued Russian attacks.

Russia on Sunday launched more than 10 rocket attacks on the Kupiansk district in the Kharkiv region, shelled more than 25 towns along the Kupiansk-Lyman front-line, and in Zaporizhzhia, hit nearly 20 towns, said Ukraine's top military command.

Russia's Defense Ministry said on Sunday that it had killed about 60 Ukrainian servicemen the previous day along the Kupiansk-Lyman line of contact and destroyed numerous pieces of Ukrainian military equipment. The reports could not be independently verified.