The funeral for Iran’s slain Supreme Leader, Ali Khamenei, entered its third day with a 12-hour procession through the streets of Tehran.

Thousands of mourners, many dressed in black and carrying banners and portraits, gathered to pay their respects before the coffin was taken to the capital’s airport.

Three of Khamenei’s sons made a rare public appearance, but his designated successor, Mojtaba Khamenei, remained absent.

Officials said Mojtaba was wounded in the airstrikes that killed his father, though the extent of his injuries remains unknown, CBS News has reported.

Authorities expect 15 to 20 million people, along with foreign dignitaries and religious leaders, to participate in the multi-day funeral ceremonies.