Public mourning ceremonies were set to begin in Iran on Saturday morning for the supreme leader, Ayatollah Ali Khamenei, a weeklong program steeped in Shiite Islamic tradition that is expected to draw tens of millions of mourners as the procession charts a sweeping path across Iran and into neighboring Iraq.

According to Iranian state media, Ayatollah Khamenei’s remains will be transported through at least five cities, starting over the weekend in Iran’s capital, Tehran, and ending on Thursday in its holiest city, Mashhad, where he was born. Along the way, the procession is expected to visit some of Shiite Islam’s most sacred shrines.

The mourning events began on Friday as foreign leaders visited the site in Tehran where his body is lying in state, the Grand Mosalla, a large prayer complex where he gave important addresses during his three decades as Iran’s supreme leader. Ayatollah Khamenei was killed on Feb. 28 at the start of the U.S.-Israeli war on Iran, and his funeral had been delayed for months because of the conflict.

Under Iran’s theocratic system of rule, Mr. Khamenei not only sat atop every branch of government but also served as the country’s highest cleric. For many of his Shiite devotees in Iran and the wider region, he was a revered figure whose death carried spiritual significance beyond politics.

The week of funerary rituals will be a logistical challenge for Iran’s regime, unfolding against the backdrop of the still unresolved war with the United States and scorching summer temperatures.

It remains unclear whether the slain leader’s son and successor, Mojtaba Khamenei, will participate in the ceremonies. He was injured in an airstrike around the same time his father was killed and has not been seen in public since then.

Here is a look at the cities where the public procession will unfold.

Tehran

Mr. Khamenei’s body will lie in state over the weekend at the Grand Mosalla, where viewing platforms have been built. At 6 a.m. on Saturday, the doors of the complex will be opened to the public. Iranian authorities have declared a public holiday.

On Monday, the coffin will be carried in a funeral procession through Tehran, marking the start of a four-day journey to Mashhad. The capital’s roads have been lined with flags emblazoned with the words “We Must Rise,” the funeral’s slogan, officials said. Some 7,000 officials are expected to stand along the route.

Officials expect around 700,000 pilgrims to take part in about 400 smaller processions in the region. To keep traffic from grinding to a halt, officials have asked mourners to park their cars on the outskirts of the capital and then proceed by public transport.

Qom

Next, the procession will travel around 100 miles south to the holy city of Qom. According to Iranian state media, Mr. Khamenei’s body will be carried on Tuesday down a grand boulevard to the Jamkaran Mosque on the city’s outskirts, where a mass prayer will be held.

The mosque holds particular significance for some Shiite Muslims because it is thought to be where a vanished imam — whose disappearance in the ninth century is a central tenet of one tradition — was last seen.

Anticipating large crowds and extreme heat, officials in Qom said they have procured 20 million bottles of water and have prepared 1.5 million sandwiches.

Iraq

Organizers have planned for the procession to cross into neighboring Iraq on Wednesday, where ceremonies are planned in the cities of Karbala and Najaf, both important historical sites for Shiite pilgrims.

Iraq is one of the few countries in the Middle East besides Iran to have a Shiite majority, and Ayatollah Khamenei’s portrait is often seen at Shiite rallies there. Though most scholars of the sect do not consider him its most important clerical authority — that is generally considered to be Grand Ayatollah Ali Sistani in Iraq — Ayatollah Khamenei had great political influence thanks to the alliances he built with Shiite militant groups around the Arab world.

Mashhad

Authorities expect more than one million mourners to join for the final leg of the procession, which will take place on Thursday in Mashhad, Iran’s second largest city.

Ayatollah Khamenei will be buried after a ceremony at the shrine of Imam Reza, where one of the twelve divine imams revered by the country’s Shiites. Imam Reza is entombed there. Ebrahimi Raisi, Iran’s former president who died in a helicopter crash in 2024, was buried in the same place.