Tens of Thousands of Iranians took part in anti-Israel rallies across the country to mark Jerusalem Day, also known as Al-Quds Day, chanting "Death to Israel" and "Death to America", while burning the Israeli flag.
The rallies, including one at Tehran University, were expected to last through Friday prayer ceremonies.
Dmonstrators protested what they called Israel’s "occupation" of Jerusalem, the city where Muslims believe Islam’s Prophet Muhammad began his journey to heaven. Palestinians want East Jerusalem for their future capital.
Iran does not recognize Israel and openly espouses its desire to destroy it. It also supports anti-Israeli terror groups such as Hamas, which rules Gaza, and Lebanon’s Hezbollah.
Demonstrators also chanted anti-American slogans to condemn the US decision to move its embassy to Jerusalem.
Iran has marked Al-Quds Day since the start of its 1979 Islamic revolution. Al-Quds is the Arabic name for Jerusalem, and Iran says the day is an occasion to express support for the Palestinians.
The speaker of Iran's parliament Ali Larijani said on Friday that security in the Middle East could be threatened if Tehran was further pressured by its arch foes Israel and Saudi Arabia.
"Israel and Saudi Arabia are the source of chaos in the region. The Saudi Arabia, Israel and American triangle wants to turn the region into a chaotic scene," state television showed Larijani telling demonstrators "The region's security will be threatened if they corner Tehran."
Israel has strongly backed President Donald Trump's decision to pull out of a 2015 international nuclear deal with Iran. Washington has re-imposed sanctions on Iran and demanded Tehran make sweeping changes from dropping its nuclear programme to pulling out of the Syrian civil war.
Supreme Leader Ayatollah Khamenei said on Monday he had ordered preparations to increase uranium enrichment capacity if the nuclear agreement collapsed despite European efforts to keep it alive.
Opposition to Israel has been a cornerstone of Iranian policy since its 1979 Islamic revolution.
"Israel is failing ... the claim of creating a new regional order is a mistake they are making and it is an illusion ... It is our responsibility to defend Palestinians," Larijani told the crowd in Tehran.
Shi'ite Iran has repeatedly called on its Sunni Muslim rival Saudi Arabia to help improve their strained bilateral relations and work for stability in the Middle East.
"The regional issues should be resolved by regional people, nations and the government," Larijani said.
Reuters and Associated Press contributed to this report.