Canada will not recognize any referendum held in the Ukrainian peninsula of Crimea as long as Russia maintains its "illegal military occupation" there, Prime Minister Stephen Harper said Thursday. "Russia's invasion of Ukraine is an act of aggression, a clear violation of Ukraine's sovereignty, and of international law. Canada will not recognize a referendum held in a region currently under illegal military occupation," Harper said in a statement from Ottawa. "We will continue to view the situation in Ukraine with the gravest concern and will continue to cooperate closely with our G-7 (Group of Seven industrial democracies) and like-minded allies," Harper wrote. The parliament of Crimea voted to join Russia on Thursday, and its Moscow-backed government scheduled a referendum on the decision in 10 days.