WATCH: Timeline: Iran’s Islamic Revolution and the 40 years that followed

Iranians are pouring out onto the streets of Tehran and other cities and towns across the country, marking the date 40 years ago that's considered victory day in the country's 1979 Islamic Revolution.

On February 11 that year, Iran's military stood down after days of street battles, allowing the revolutionaries to sweep across the country while the government of Shah Mohammad Reza Pahlavi resigned.

Crowds were marching on Monday, heading out from a dozen points in the Iranian capital toward Tehran Azadi, or Freedom Square.

Tehran's downtown Enghelab, or Revolution Street, is decorated with huge balloons. Loudspeakers are blaring out revolutionary and nationalist songs to encourage people to join the rallies.

This year's anniversary come as tensions are rising with the US and Iran is grappling with re-imposed US sanctions.

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