The rallies are held to mark Quds Day, which falls on the last Friday of the Muslim fasting month of Ramadan.
The occasion is a legacy of the late founder of the Islamic Republic Imam Khomeini, followed by Muslims in other countries to support the Palestinian struggle against Israel.
Leader of the Islamic Revolution Ayatollah Seyyed Ali Khamenei has emphasized the importance of Quds Day.
“It is not just that we are defending an oppressed nation that has been driven out of its home. We are actually fighting against an oppressive and arrogant political system,” Ayatollah Khamenei said.
Iranian President Hassan Rouhani along with other senior Iranian officials took part in the Tehran rally.
Speaking on the sidelines of the event, Rouhani said “the message of Quds Day is that of hatred towards the occupying and usurping regime as well as support for the oppressed nation” of Palestine.
In Tehran and other cities and towns, people from all walks of life gathered for the annual event which usually marks people chanting slogans against Israel and burning the occupying regime's flags.
He underlined the importance of this year’s Quds Day “given the presence of terrorists in the region, who are backed by Israel,” adding people are determined to cleanse the region of Tel Aviv-backed terrorists.
Rouhani said the high turnout in the demonstrations also serves as a response to the United States, which has recently been seeking to pile pressure on Iran by tightening its sanctions.
During the rallies in the capital, Iran also put on display three surface-to-surface ballistic missiles, including the Zolfaghar, the type that Iran used this week to destroy Daesh positions in Syria.