In commemoration of opposition leader Boris Nemtsov, who was shot to death on Friday, thousands are marching in central Moscow on Sunday. Nemtsov killed after urging people to protests against Vladimir Putin and the war in Ukraine. The march was approved by city officials on Saturday with a permit of up to 50,000 people. Putin has publicly promised to find and prosecute those who killed Nemtsov. "Everything will be done to give the organizers and executors of this base and cynical murder the punishment they deserve," he promised in a note of condolence to Nemtsov's mother, Dina Eidman. However, weeks before Nemtsov claimed that Putin wanted him dead.