Thousands of mourners gathered at Imam Khomeini Mosalla Grand Mosque in the Iranian capital Tehran on Saturday as week-long funeral rites for the country's slain Supreme Leader Ayatollah Ali Khamenei got underway.

The funeral ceremonies began with the national anthem, Quran recitations and religious eulogies, Iran's state broadcaster IRIB reported.

Khamenei's coffin was placed on public display in a glass case for mourners to pay their respects, according to the broadcaster.

Khamenei was killed in US-Israeli strikes on Iran that began on Feb. 28, followed by Iranian retaliatory attacks.

Citing Iran's national airline, the report said special flights were added on the Tehran-Mashhad route to meet "increasing demand for travel" by people attending the funeral rites.

The funeral ceremonies officially began Friday, with foreign leaders and official delegations from across the region and beyond paying tribute to the late Iranian supreme leader.

Among the senior foreign dignitaries attending were Russian Security Council Deputy Chairman Dmitry Medvedev, Turkish Vice President Cevdet Yilmaz, Iraqi President Nizar Amidi, Iraqi Parliament Speaker Mohammed al-Halbousi, Pakistani Prime Minister Shehbaz Sharif, Pakistani Senate Chairman Yousaf Raza Gillani, and Pakistani Army Chief Asim Munir.

According to the official schedule, memorial ceremonies will continue in Tehran through the weekend with the participation of heads of state, senior officials and religious figures.

Public farewell ceremonies are scheduled for July 4 and July 5, followed by the main funeral procession in Tehran on July 6.

The funeral rites will then move to Qom on July 7.

On July 8, ceremonies are scheduled in Iraq, including in Baghdad, Najaf and Karbala, where the body will be received by religious and political figures before being transferred to major Shia shrines.

The final funeral and burial ceremony is scheduled for July 9 at the Imam Ali Reza Shrine in the northeastern city of Mashhad, one of Shia Islam's holiest sites. (AA)