A top political nemesis of President Vladimir Putin was shot and killed early Saturday in central Moscow, Russian police said, one day before an opposition rally was scheduled to take place. Boris Nemtsov, 55, a former deputy prime minister, was shot four times from a passing car as he was walking on a bridge just outside the Kremlin. Interior Ministry spokeswoman Yelena Alexeyeva told reporters on the scene that Nemtsov was walking with a female acquaintance, a Ukrainian citizen, when a vehicle drove up and unidentified assailants shot him dead. The woman wasn't hurt.