Russia says three military servicemen were killed by falling debris Monday after a Ukrainian drone was shot down as it approached an air base used to launch attacks on Ukraine. It was the latest in a series of attacks by Ukraine deep inside Russian territory. In Ukraine, fighting continued over the weekend after calls for a Christmas ceasefire went unheeded. Ukraine’s government says Russian artillery fire killed 10 people and injured dozens more on Christmas Eve in the city of Kherson, which was recaptured by Ukraine last month. Russian attacks on the power grid left some 9 million people without electricity over the holiday weekend. On Sunday, Russian President Vladimir Putin said he was prepared to negotiate to end the war in Ukraine, adding, “It’s not us who refuse talks, it’s them.” Ukraine’s foreign minister, meanwhile, called on the U.N. to convene a peace summit with Secretary-General António Guterres as mediator.