He is being laid to rest in his hometown of Kerman, with millions already estimated to have packed the streets for funeral processions.
An Iranian general warned that the “martyr” Qasem Soleimani was more dangerous dead than alive.
The killing has raised fears of a conflict between the US and Iran.
Soleimani was widely considered the second most powerful man in Iran behind Supreme Leader Khamenei. The US saw him as a terrorist and a threat to American troops.
In other developments:
The US has reportedly denied a visa for Iranian Foreign Minister Javad Zarif to visit the UN in New York later this week. Such a move would apparently breach an agreement guaranteeing foreign officials access to the UN headquarters.
Germany is withdrawing a small number of soldiers stationed in Iraq as part of the coalition fighting Islamic State.
The US denied it was pulling out of Iraq, after a letter from a US general suggested there would be a withdrawal.
Iranian parliamentarians have approved a motion designating the US Army and the Pentagon as terrorist organisations.
In Kerman, south-eastern Iran, vast numbers of people were again seen in the streets with Soleimani’s body due to be buried shortly.
“The martyr Qassem Soleimani is more powerful… now that he is dead,” said the Revolutionary Guards’ top general, Major General Hossein Salami.
The Guards were set up to defend Iran’s Islamic system and is a major political and military force.
Mourners chanted “death to America” and “death to Trump”, reporters there said.
“He [Soleimani] was seen as a great man who was ready to serve his people… He must certainly be avenged,” an 18-year-old student who was there told the AFP news agency.
On Monday, Ayatollah Khamenei led prayers at Soleimani’s funeral in Tehran, at one point weeping over his coffin.
Unconfirmed estimates from Iranian state television put the number who took to the streets of Iran’s capital alone as “millions”. The crowds were large enough they could be seen in satellite images.
Who was Qasem Soleimani?
Soleimani was head of the Quds force, the overseas branch of the Revolutionary Guards. He was killed leaving Baghdad airport on Friday.
In his homeland, Soleimani was hailed as a national hero.
But he was also hardliner and a dominant force in a state that shot dead scores of protesters at the end of 2019.
Soleimani supported Syria’s President Bashar al-Assad in the country’s civil conflict, aided the Shia militant group Hezbollah in Lebanon, and guided Iraqi militia groups against the Islamic State group.
Justifying the strike President Trump said Soleimani was plotting “imminent” attacks on US diplomats and military personnel.
What has happened since his death?
Immediately after his death Iran threatened retaliation and officials have kept up the rhetoric.
On Sunday, Iran declared it would no longer abide by any of the restrictions imposed by the 2015 nuclear deal. The deal limited Iranian nuclear capacities in exchange for the lifting of economic sanctions.
Following warnings from Iran, Mr Trump said that the US would respond in the event of retaliation for Soleimani’s death, “perhaps in a disproportionate manner”.
Trump administration officials though have contradicted the US president on his controversial threat to target Iranian cultural sites.
Such acts could be considered war crimes and Secretary of Defence Mark Esper said “we will follow the laws of armed conflict”.