Trucks carrying the bodies of former Supreme Leader Ayatollah Ali Khamenei and his family arrived on Thursday in Mashhad, where Iran's holiest shrine is located.
They are expected to be buried during the day, in a personal ceremony where only the family will be allowed to participate.
While his son and successor, Mojtaba Khamenei, is still hidden from public view after being reportedly disfigured in the strike that killed his father, his other three sons are expected to assist after being present in the processions made along the country.
The burial in Mashhad in northeast Iran follows a week of mass funeral processions, rallies and mourning ceremonies that have coincided with a renewed burst of conflict with the United States following weeks of truce.
Khamenei's body was carried by truck slowly through the crammed Mashhad streets towards the gilt dome and minarets of the Shrine of Imam Reza, flanked by white-turbaned clerics walking on either side. Black-clad mourners pressed in close behind, waving Iranian flags, photographs of the late Khamenei and red placards with revolutionary slogans.
The burial will be the culmination of a week of funeral events in both Iran and Iraq that the Islamic Republic's clerical leaders have been encouraging huge crowds to attend in an effort to vaunt the might and ideological fire of their theocratic state.
However, despite it having survived a months-long blitz by its strongest enemies, the United States and Israel, Iran faces huge internal challenges, and the legacy of Khamenei's 37-year rule is bitterly disputed.
Mojtaba Khamenei's whereabouts remain a mystery
The whereabouts of Mojtaba Khamenei, proclaimed Supreme Leader by a clerical assembly a week after his father's death, have remained a mystery to Iranians.
He has not appeared in public since the war began with the strike that killed his father on February 28, and while he has issued written statements, no image, video, or voice recording of him has been shared by the regime.
According to the regime's officials, he suffered debilitating injuries in that same strike, his face was disfigured, and his limbs were badly wounded.
Senior sources in Tehran have said he is recovering but that he has not yet been well enough to manage public appearances and state security services are also trying to limit his exposure in case of more US attacks.
'Kill Trump' placards appear at burial ceremony
As crowds jostled in Mashhad awaiting Khamenei's funeral cortege, the crowd chanted slogans demanding revenge on US President Donald Trump for his killing.
“I swear by the blood of the Supreme Leader, Trump, we will kill you!” they shouted, with women holding up placards reading "Kill Trump."
The roads leading to the shrine were a sea of black-clad mourners on Thursday, some responding to shouted chants in praise of Khamenei and against Iran's enemies, including the old revolutionary slogan of "Death to America."
As the crowds awaited the coffins of Khamenei and his family in the sweltering July heat, hoses pumped water high into the air to spray across the mourners and keep them cool.
Khamenei's remains, along with those of four family members killed alongside him, have already been paraded through Tehran, the Shi'ite Muslim clerical center of Qom, and the Iraqi shrine cities of Najaf and Karbala.
At each event, huge crowds have thronged the streets to the mournful accompaniment of sung Shi'ite laments and chanted revolutionary slogans.
Martyrdom holds a central place in Shi'ite theology, and Khamenei's death at the hands of foreign enemies has played into a religious and political tradition that runs deep through the Islamic Republic.