By Michelle Nichols, Humeyra Pamuk and Daphne Psaledakis UNITED NATIONS (Reuters) -Russia’s top diplomat on Saturday said regions of Ukraine where widely-derided referendums are being held would be under Russia’s “full protection” if they are annexed by Moscow, amid fears Russia could further escalate the conflict and even use nuclear weapons. Foreign Minister Sergei Lavrov, addressing the U.N. General Assembly and the world’s media in New York, attempted to justify Russia’s February invasion of its neighbor, repeating Moscow’s false claims that the elected government in Kyiv was illegitimatel…