Thousands of Iranians massed on Tuesday for commemorations marking 41 years since the Islamic Revolution, in a show of unity at a time of heightened tensions with the United States.
The celebrations mark the day that Shiite cleric Khomeini returned from exile and ousted the Shah's last government.
The state has appealed for a strong turnout as a show of solidarity after a year in which Iran has been shaken by protests and military tensions with the United States.
Iran almost got into a full-blown conflict with the United States last month after a US drone strike killed top Iranian military commander Qassem Soleimani in Baghdad on January 3, prompting Iran to retaliate with a missile barrage against a US base in Iraq days later.
Tensions spiked between Iran and the United States after US President Donald Trump withdrew from a multilateral nuclear deal with Iran in 2018 and reimposed sanctions in a bid to pressure Tehran to negotiate over its ballistic missile programme and ties with regional proxy groups.