Soleimani receives hero's welcome as millions flood Iran streets
As Shia chants resonated in the air, mourners held portraits of Soleimani, seen as a hero of the 1980-88 Iran-Iraq war and for spearheading Iran's Middle East operations as commander of the Revolutionary Guards' Quds Force.
Millions of mourners dressed in black were seen gathered in Ahvaz in a live broadcast on state television.
The channel showed crowds in Mollavi Square with flags in green, white and red - depicting the blood of "martyrs".
"A glorious crowd is at the ceremony," said state television.
"The presence of children, teenagers, relatives, veterans, families of martyrs of (the Iran-Iraq war) and defenders of the Haram (those martyred defending shrines) is a glimpse of the glory of this ceremony," it added.
Soleimani's remains and those of five other Iranians - all Guards members - killed in the US drone strike had arrived at Ahvaz airport before dawn, ISNA said.
Comment: Soleimani assassination spells trouble for Iraqis, Iranians and the region
With them were the remains of Abu Mahdi al-Muhandis, the deputy commander of Iraq's powerful Hashd al-Shaabi paramilitary umbrella group, who was also killed in the US strike.
They are expected to be flown to Tehran for more tributes on Sunday evening.
On Monday, Khamenei is expected to pray over Soleimani's remains at Tehran University before a procession to Azadi Square.
His remains are then due to be taken to the holy city of Qom for a ceremony at Masumeh shrine, ahead of a funeral Tuesday in his hometown Kerman.
Soleimani was killed at the age of 62 in a US drone strike on Friday near Baghdad airport, shocking the Islamic republic.
The attack was ordered by President Donald Trump, who said the Quds commander had been planning an "imminent" attack on US diplomats and American forces in Iraq.
In the face of growing Iraqi anger over the US strike, the country's parliament was expected to vote on Sunday on whether to oust the roughly 5,200 American troops in Iraq.
Soleimani's assassination ratcheted up tensions between arch-enemies Tehran and Washington and sparked fears of a new Middle East war.
Iran's supreme leader Ayatollah Ali Khamenei vowed "severe revenge" and declared three days of mourning.
Read more: Who was Qasem Soleimani, the powerful commander of Iran's elite Quds force?
But Trump warned late on Saturday that America was targeting 52 sites "important to Iran & Iranian culture" and would hit them "very fast and very hard" if the country attacks American personnel or assets.
In a series of sabre-rattling tweets, Trump said the choice of 52 targets represented the number of Americans held hostage at the US embassy in Tehran for more than a year starting in late 1979.
Iran's top diplomat Mohammad Javad Zarif tweeted that "targeting cultural sites is a WAR CRIME" and a red line in international law.
For Iran's army chief, the threat was an attempt to distract the world from Soleimani's "unjustifiable" assassination.
"I doubt they have the courage to initiate" a conflict in the future, said Major General Abdolrahim Mousavi.
"We will eventually see who will receive strikes on 52 targets", Iran's army chief warned.
US-Iran tensions escalated in 2018 when Trump unilaterally withdrew from a landmark accord that gave Tehran relief from sanctions in return for curbs on its nuclear programme.
Iran has hit back by reducing its nuclear commitments with a series of steps every 60 days, the most recent deadline passing on Saturday.
Meanwhile in Tehran, deputies chanted "Death to America" for a few minutes during a regular session of parliament, semi-official news agency ISNA reported.
"Trump, this is the voice of the Iranian nation, listen," speaker Ali Larijani was quoted as saying.
In neighbouring Iraq, pro-Iran factions ramped up pressure on US installations with missiles and warnings to Iraq's troops.
In the first hints of a possible retaliatory response, two mortar rounds struck near the US embassy in Baghdad, security sources said on Saturday.
Almost simultaneously, two rockets slammed into the Al-Balad airbase where American troops are deployed.
Iraq's military confirmed the missile attacks in Baghdad and on Al-Balad and said there were no casualties. The US military also said no coalition troops were hurt.
Agencies contributed to this report.
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