The area is packed with people. Some walk several kilometres to get to the site. Participants shout “death to America” and “revenge.” Many are dressed in black and carry red flags, which are seen as a call for revenge and justice. Signs throughout the city bear Khamenei’s image.
Mourners cry at the sight of Khamenei's coffin.
Imam Khamenei was our heart, our father, our everything, says Masoumeh Mohammadi, who is attending the ceremony.
I still can't believe they made him a martyr. We won't rest until we avenge his death.
Looking for the son
During the days leading up to the ceremony, the world is keeping an eye out for Khamenei's son, Mojtaba Khamenei. He was appointed supreme leader a week after his father was killed in February. However, so far he has not appeared in public, communicating only in writing.
Mojtaba Khamenei is said to have been injured, but the extent of the injury is unclear.
Organisers are spraying water on the crowds and offering cold drinks to help people cope with the summer heat. Visitors are being checked with metal detectors and body searches. Police with assault rifles stand guard on the surrounding streets.
On the outdoor stage, the coffin said to contain the remains of Ayatollah Ali Khamenei is visible, and beneath it are coffins for his family members who were also killed.
"We came because we promised the Supreme Leader that we would stand by his side until the end," says 37-year-old university professor Reza.
The delegation from the Lebanese Hezbollah movement is led by former minister Mohammed Fneish. The group from the Palestinian Hamas is led by the head of the political bureau, Mohammed Darwish.
Many millions
Khamenei will remain at the helm of the parade until Monday, when a procession will pass through the capital Tehran. According to Iranian authorities, many millions of people are expected to participate in Tehran alone over the next three days.
Extensive traffic restrictions have been imposed for the mourning period. The funeral of the ayatollah, who was killed in US-Israeli strikes in connection with the outbreak of war in February, is set to last six days. Several family members and high-ranking officials were also killed in the attack.
Khamenei's body will be taken to cities in both Iran and neighbouring Iraq as part of the ceremony. The actual burial will then take place on Thursday in Khamenei's hometown of Mashhad.
Ali Khamenei ruled Iran from 1989 until his death at the age of 86.
