The mass rallies in Tehran are held concurrently with the nationwide demonstrations to condemn the atrocities and crimes committed by Israel against people of Palestine, particularly those under fire in the besieged Gaza Strip.
Carrying placards and chanting slogans against Israel and the US, marchers gathered in front of Tehran University.
Protesters in Tehran also voiced their support for the people of Gaza and opposition to the occupation of the Palestinian territories by the Zionist regime.
The high turnout of people in the rallies came after Supreme Leader of the Islamic Revolution Ayatollah Seyed Ali Khamenei on Wednesday evening described political support for the people of Gaza as a duty for all Muslim and non-Muslim nations.
The Leader had also called for massive demonstrations to express solidarity with Palestinian people on the International Quds Day.
On Wednesday, the Iranian Foreign Ministry also issued a statement, calling on the Iranian people, all the Muslims and all the freedom-seekers of the world to massively demonstrate on the International Quds Day to express their hatred towards the occupiers of Palestine.
Each year, the International Quds Day is celebrated on the last Friday of the holy Muslim month of Ramadan.
The event’s overarching theme is support for the Palestinians and fierce denunciation of Israel.
The day is also seen as the legacy of the late founder of the Islamic Republic of Iran, Imam Khomeini, who officially declared the last Friday of the holy month of Ramadan as International Quds Day back in 1979.
This year's rallies came against the backdrop of a massive Israeli onslaught on the besieged Gaza Strip.
Over 800 Palestinians have been killed and more than 5,200 have been injured in 18 days of Israeli attacks.