DUBAI, United Arab Emirates — Protests in Iran raged Friday night in the Islamic Republic, online videos purported to show, despite a threat from the country's theocracy to crack down on demonstrators after shutting down the internet and cutting telephone lines to the world off. At least 65 people have been killed in the protests that began in late December over Iran’s ailing economy and have morphed into the most significant challenge to the government in years. Supreme Leader Ayatollah Ali Khamenei dismissed U.S. President Donald Trump as having hands “stained with the blood of Iranians” as his supporters shouted “Death to America!” in footage aired by Iranian state television. State media later referred to the demonstrators as “terrorists,” setting the stage for a violent crackdown as in other protests in recent years, despite Trump's pledge to back peaceful protesters with force if necessary. Protesters are “ruining their own streets ... in order to please the president of the United States,” the 86-year-old Khamenei said to a crowd at his compound in Tehran. “