TEHRAN : Prayers were to be said over the casket of slain Iranian supreme leader Ali Khamenei on Sunday, the second day of marathon funeral ceremonies that have already drawn huge crowds to pay their final respects in Tehran.

Authorities have not announced whether a religious figure or a family member will lead the prayers for Khamenei, who ruled Iran from 1989 until he was killed aged 86 in an airstrike on the first day of the Middle East war on February 28.

His son and successor Mojtaba Khamenei has not been seen in public since being named supreme leader, and is said to have been wounded in the same attack.

Sunday has been declared a public holiday for the entire country, and in the evening, Khamenei's body will leave the Grand Mosalla complex where it is lying in state in preparation for processions through the capital planned for Monday.

Hassan Hassanzadeh, in charge of the ceremonies as commander of the powerful Revolutionary Guards in Tehran, said that "prayers will be carried out over the holy body of the martyred leader" at 8:00 am local time (0430 GMT), according to state TV.

On Saturday, vast crowds of Iranians loyal to the Islamic republic had massed for the start of the public funeral ceremonies, which authorities hope will serve as a message of defiance after the war with the US and Israel.

Clad in black and waving blood-red flags symbolising vengeance and justice, mourners beat their chests in a sign of grief as chants of "death to America" and "revenge, revenge" echoed around the venue.

"The leader was a father to us all. With his passing, we have all been left orphaned," said Mohammad Mirsalehi, 38, a cleric.

The coffins of Khamenei, with his black turban on top, and four family members also killed in the February 28 strikes -- including his infant granddaughter -- were placed at the front on a raised dais, AFP photographs showed.

Authorities believe the ceremonies will mobilise more than 10 million people in the capital alone.

- Allies in attendance -

After five weeks of intense hostilities, the Middle East war is on hold after a ceasefire and an initial accord with the US. But both Washington and Tehran have warned they are ready to resume fighting at any time.

Khamenei's funeral is being viewed outside Iran as a test of support for the government following mass protests before the war in January that rights groups say were quelled by a crackdown that left thousands dead.

"What is observed today in the emotions, tears, and passionate presence of the people in various scenes is the most telling sign of his position among the Iranian nation and the free people of the world," President Masoud Pezeshkian said in a speech Saturday, accusing Israel in particular of acting as a "destabilising factor" in the Middle East.

"Muslims have shown that they will not surrender to oppression and bullying," he added.

Khamenei had long pursued a course of confrontation with the West, and Tehran for years has provided support to anti-US and anti-Israel armed groups around the region, including Palestinian Hamas and Lebanon's Hezbollah.

Delegations from both groups met with Foreign Minister Abbas Araghchi on Saturday, state media reported, while representatives of Yemen's Houthi rebels and Hamas ally Palestinian Islamic Jihad were also in attendance at the funeral.

After Monday's procession, Khamenei's coffin will be moved on Tuesday to the clerical city of Qom, then on Wednesday to neighbouring Iraq, before the burial on Thursday in his northeastern hometown of Mashhad.

Significant security measures have been imposed in the capital, and official media has warned attendees of the risk of crowd crushes.

Organisers have also taken measures to mitigate a heatwave that may nudge 40C in Tehran over the next few days, with crowds on Saturday sprayed with mists of water to keep cool at the Grand Mosalla complex.