The message, broadcast widely in Iranian media, urged people to join religious groups "in the squares of all the country's cities from 5:00 pm (1330 GMT)".

It said it would be a "popular gathering to neutralise the potential plots of elements of the Zionist enemy", referring to Israel.

The call came after Israel said it had killed Iran's security chief Ali Larijani, which has not been confirmed by Tehran, and ahead of expected evening celebrations of Chaharshanbe Suri, an ancient Iranian festival of light and fire marked before the new year, Nowruz.

Reza Pahlavi, the eldest son of Iran's last shah ousted by the revolution that brought the Islamic republic to power, on Tuesday called for peaceful Chaharshanbe Suri celebrations and for people to "avoid any tension, confrontation, or even approaching" security forces in the streets.

Iran was rocked by mass protests that peaked in January but were met with a violent crackdown.

Since the outbreak of the war, authorities have warned against renewed anti-government rallies and imposed heavy security measures.

US and Israeli leaders have in turn called on Iranians to be ready to rise up against the clerical leadership.

Judicial authorities in the capital Tehran on Sunday warned people not to go into the streets as usual for Chaharshanbe Suri.

"To maintain public peace and safety, please refrain from lighting fires or setting off firecrackers" for the holiday, they said, according to the Tasnim news agency.

"Let's keep forces available for possible and necessary incidents," they added.

Iranian officials had also earlier called on citizens to join the funeral ceremonies on Tuesday of 84 navy sailors killed when their frigate was sunk by a US submarine.

Israel and the United States launched strikes on Iran on February 28, killing the Islamic republic's supreme leader, Ali Khamenei, and triggering a conflict that has spread across the Middle East.