TEHRAN, Iran — Iran’s supreme leader on Tuesday blamed the protests roiling the country on “enemies of Iran” who he said were meddling in its internal affairs, as state television reported that overnight clashes between protesters and security forces killed another nine people. The demonstrations, the largest seen in Iran since its disputed 2009 presidential election, have brought six days of unrest across the country and resulted in at least 21 deaths. The protests began Thursday in Mashhad over Iran’s weak economy and a jump in food prices.