The procession is scheduled to visit the holy Shiite city of Karbala before heading to the nearby holy city of Najaf, some 160 km south of Baghdad, where the dead will be buried in the huge Wadi al-Salam cemetery.

Early on Friday, a US drone attack ordered by President Donald Trump killed Soleimani, commander of the Quds Force of Iran's Islamic Revolution Guards Corps, and the Iraqi militia commander al-Muhandis.

The attack took place on the road leading to Baghdad International Airport.

Iran's Supreme Leader Ayatollah Ali Khamenei and President Hassan Rouhani have vowed to retaliate against the United States over Soleimani's death.

Friday's attack came just days after Iraqi protesters stormed the US embassy in Baghdad over the US air raids on Dec 29 against five bases of Iran-backed militias in Iraq and Syria that claimed the lives of 25 militants.