Funeral ceremonies for Ayatollah Ali Khamenei began on Saturday in Tehran, where large crowds gathered at the Grand Mosalla Mosque to pay tribute, Iranian state media reported.

Official statements say Khamenei’s body is lying in state at the Grand Mosalla before a series of funeral events planned for several Iranian cities. Officials forecast millions could take part in the commemorations in the coming days, but those figures could not be independently verified.

Many of the attendees wore black and chanted pro-government slogans during the opening ceremony, according to international news agencies.

One mourner, identified by AFP as 37-year-old professor Reza, said he had come to honour Iran’s former supreme leader.

We came because we promised the supreme leader we would be with him to the end,” he said.

“I think people who came here wanted to remember the legacy of Khamenei after his death,” Arash Rahimi, another participant,

The funeral follows reports that Khamenei was killed in military strikes earlier this year, an event that greatly heightened tensions across the Middle East. The precise circumstances of his death are at the heart of continuing regional and international developments.

The authorities said the body would stay in Tehran for several days before being moved to other religious sites, including Qom and Mashhad, where funeral ceremonies are planned to end later this week.

Security has been increased in central Tehran and traffic restrictions and more police are expected across the period of the funeral

The ceremonies are expected to continue after the burial, with more commemorative events planned across Iran in the coming weeks.