Alexander Timofeev, another rebel leader, was seriously injured, said a statement released by the separatists. Russian President Vladimir Putin, in a statement, called Zakharchenko a patriot and his death a "vile murder" intended to destabilize the region. A top Russian law enforcement body, the Investigative Body, said it had opened a criminal investigation of the killing as a suspected act of international terrorism. Foreign Ministry spokeswoman Maria Zakharova blamed Zakharchenko's death on the Ukrainian government. The Ukrainian government declined comment. Ukraine has accused Moscow of being behind a string of assassinations on Ukrainian soil.