Large crowds gather in Tehran to hear speech by President Mahmoud Ahmadinejad.
Hundreds of thousands of Iranians on Monday shouted "death to America" and pledged their loyalty to the Islamic republic as they celebrated the 29th anniversary of the Islamic revolution.
Large crowds of people were converging on Azadi square in Tehran from points across the city to hear a speech later by President Mahmoud Ahmadinejad, braving cold and misty weather in the capital.
"Down with the USA!" read placards carried by the demonstrators.
"I sacrifice myself for the leader" Ayatollah Ali Khamenei, said another banner carried by demonstrators.
Similar demonstrations were taking place up-and-down the country and Iranian television showed large crowds gathering in the southeastern provincial capital Kerman.
"Israel is an enemy of Islam! Israel is an enemy of humanity!" said one placard in Kerman in reference to Iran's main regional enemy, television pictures showed.
The national holiday of the "glorious victory of the Islamic revolution" marks the day on February 11, 1979 when the army refused to continue fighting the anti-shah popular uprising led by Ayatollah Ruhollah Khomeini.
The army's decision effectively handed control of the country to Khomeini and spelled the end for the shah's last prime minister Shapur Bakhtiar. Pro-US Shah Mohammad Reza Pahlavi had left Iran three weeks earlier.
Khomeini had returned from his exile in France just 10 days before and already appointed Mehdi Bazargan as interim prime minister. Bazargan would lead Iran's first post revolutionary government.
State television has been broadcasting archive footage and patriotic songs for this year's rallies, which come a month ahead of parliamentary elections and amid the standoff with the West over Iran's nuclear drive.