Russian President Vladimir Putin on Friday ordered his military to prepare options to retaliate against Ukraine for what he described as a drone attack on a student dorm that killed six people and wounded dozens, with 15 still unaccounted for. Putin said the attack had struck the dorm in Starobilsk in Luhansk, a Russian-controlled region in eastern Ukraine. He said Kyiv’s military must have known what it was targeting. Ukraine’s military denied the Russian accusations and said it had struck an...