Thousands of Iranians chanting "Death to America" marked the anniversary on Friday of the 1979 seizure of the US embassy amid references to recent US allegations of an Iranian assassination plot.

The annual celebration in front of what Iranians call "the den of spies" was also used this year as a platform to hail the Arab Spring -- termed the "Islamic awakening" here -- and to denounce Israel.

On November 4, 1979, months after the Islamic revolution that overthrew the US-backed shah, Mohammad Reza Pahlavi, students stormed the embassy and took 52 US diplomats hostage in a crisis that lasted 444 days.

The hostage-taking resulted in the breaking of diplomatic relations between Iran and the United States and has left the two countries implacable foes for the past 32 years.

Tensions intensified last month after the United States accused Iranian officials of masterminding a plot to assassinate the Saudi ambassador to Washington.

Tehran which has vehemently denied any involvement has sent a letter to Washington demanding an apology.

The former embassy, which is painted with anti-US murals, has become a training and educational facility under the control of the elite Revolutionary Guards.