Tehran funeral procession begins for slain Supreme Leader Ali Khamenei

The funeral procession for Iran's late Supreme Leader, Ali Khamenei, is now under way in Tehran, with officials preparing for crowds that could approach the scale of his predecessor's send-off nearly four decades earlier.

Khamenei's body lay in state for two days at the Grand Mosalla religious complex in the capital before the Monday march through Tehran, where large numbers of mourners joined the route, state broadcaster IRIB reported. He was killed on the first day of the United States-Israel war on Iran, in air strikes on his office in Tehran on February 28.

On Sunday, thousands gathered at the Grand Mosalla to honour Khamenei and four family members who died alongside him in the same attack.

Authorities say they want to avoid a repeat of the disorder that marked the 1989 funeral of Ruhollah Khomeini, Khamenei's predecessor. State news agency IRNA has put attendance at that event at an estimated 10 million people. Surging crowds during Khomeini's funeral killed more than 10 people and left more than 10,000 injured.

After Monday's procession in Tehran, further ceremonies are set for the clerical centre of Qom on Tuesday, Iraq's holy cities of Najaf and Karbala on Wednesday, and burial in Khamenei's northeastern hometown of Mashhad on Thursday.