Hundreds of thousands flooded the streets of Tehran to denounce the United States in the Islamic Republic's "day of rage."
Video shown on Fox Business Network showed some demonstrators burning American and Israeli flags and chanting "death to America."
The "day of rage" takes place each year in Iran to mark the anniversary of the 1979 Islamic revolution.
It comes just a week after the White House declared that Iran was "on notice" and imposed new sanctions on the regime following the test-launch of a ballistic missile.
Iran test-fired a short-range surface-to-air missile two days ago and is continuing with its confrontational rhetoric toward the Trump administration.
A foreign policy adviser to Iran's supreme leader told Al Jazeera Thursday that America will face "dark days" if it attacks Iran.
"Washington does not dare carry out its military threats against Iran. The Americans know very well that Iran and its allies in the region would retaliate very hard. That will make America face dark days to come," said Ali Akbar Velayati.
Watch the report above.