TEHRAN (AFP) - Thousands of Iranians chanting "Death to America" marked the anniversary on Friday of the 1979 seizure of the US embassy with symbolic actions and speeches condemning 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. Some of the mainly young crowd taking part burnt US and Israeli flags and a picture of US President Barack Obama. Effigies of Israeli and US political figures were held aloft. Saeed Jalili, secretary of the Supreme National Security Council, told the demonstrators the government had "irrefutable" evidence of the United States "backing, training terrorists" against Iran. He waved some papers and said they were documents backing his claims. He did not give further details but said Iran's ambassador to the United Nations would submit the papers to UN chief Ban Ki-moon in order "to take needed action against these impudent acts." Tensions between Iran and the United States intensified last month when US officials accused Tehran of masterminding a plot to assassinate the Saudi ambassador to Washington. Iran has fiercely denied any involvement in the alleged assassination plot and sent a letter to Washington demanding an apology. It has called the accusations an attempt by the United States to distract attention from domestic economic problems and a failed policy in the Middle East. Jalili lauded by name Qasem Soleiemani, the head of Iran's elite Quds Force special operations unit, whom US officials identified as a key figure in the alleged assassination plot. In words addressed to the United States, Jalili said: "With the backing of the people, one of the commanders of the sacred defence forces, Qasem Soleiemani, is enough to put you in your place." Iran on Thursday made a formal protest to the United States, through the Swiss embassy that handles US interests, about testimony to a Congressional committee last week by two defence analysts urging the targeted assassination of Soleimani and other members of the Quds Force. The two analysts -- retired four-star general Jack Keane, who helped plan the US-led occupation of Iraq, and former CIA officer Reuel Marc Gerecht, now a senior fellow at neo-conservative think-tank the Foundation for Defence of Democracies, were invited to speak as expert witnesses. Friday's demonstration commemorated November 4, 1979, when Islamic students stormed the US embassy in Tehran 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. 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. Demonstrators on Friday also carried banners supporting the "Occupy Wall Street" movement and denouncing capitalism.