Mass protests in the streets of Iran are presenting the most significant challenge to the country’s regime in years. President Trump today renewed his threat to take action in Iran if the government there goes after protestors.

"It is difficult to discount the role of the U.S. government in shaping the current moment," one Iran expert told Newsweek.

Supreme Leader Ayatollah Ali Khamenei had earlier dismissed Trump as having hands “stained with the blood of Iranians”.

Iran's judiciary chief has vowed decisive punishment for protesters, signaling a coming crackdown against demonstrations.

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