A tide of mourners wept and beat their chests in the Iranian city of Ahvaz on Sunday, paying homage to top general Qasem Soleimani, after he was killed in a US strike in Baghdad.
"Death to America," they chanted at a mass gathering in the southwestern city, where Soleimani's remains arrived from Iraq before dawn, according to semi-official news agency ISNA.
Packing the streets as Shiite chants resonated in the air, mourners held up 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.
Soleimani was killed in a US drone strike on Friday near Baghdad international airport, shocking the Islamic republic. He was 62.
The air strike was ordered by President Donald Trump, who said the Iranian general had been planning an "imminent" attack on US diplomats and the roughly 5,200 American troops deployed in Baghdad.
Soleimani's assassination ratcheted up tensions between the arch-enemies and sparked fears of a new war in the Middle East.
Iran's supreme leader Ayatollah Ali Khamenei swiftly vowed "severe revenge" and declared three days of mourning.
But Trump warned Saturday that America was targeting 52 sites in Iran and would hit them "very fast and very hard" if the Islamic republic attacks American personnel or assets.
In a sabre-rattling tweet, Trump said: "If they attack again, which I would strongly advise them not to do, we will hit them harder than they have ever been hit before!" 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.
US-Iran tensions escalated last year when Trump unilaterally withdrew from a landmark accord that gave Tehran relief from sanctions in return for curbs on its nuclear programme.
On Sunday, thousands of mourners dressed in black were seen gathered in the southwestern Iranian city of Ahvaz in a live broadcast on state television.
The channel showed crowds gathered in Mollavi Square with flags in green, white and red -- depicting the blood of "martyrs".
Aerial footage showed a tide of mourners crammed into the square and the surrounding streets of downtown Ahvaz, a city of 1.3 million people.
"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 Haram (those martyred in Syria) is a glimpse of the glory of this ceremony," it added.
In Tehran, members of parliament chanted "Death to America" for a few minutes during a regular session, ISNA reported.
"Trump, this is the voice of the Iranian nation, listen," speaker Ali Larijani was quoted as saying.
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. With them were the remains of Abu Mahdi al-Muhandis, the deputy commander of Iraq's powerful Hashed 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 in his hometown Kerman on Tuesday.
In neighbouring Iraq, pro-Iran factions ramped up pressure on US installations with missiles and warnings to Iraqi troops -- part of an outburst of fury over the killing of Soleimani.
In the first hints of a possible retaliatory response, two mortar rounds struck an area near the US embassy in Baghdad on Saturday, security sources told AFP.
Almost simultaneously, two rockets slammed into the Al-Balad airbase where American troops are deployed, security sources said.
The Iraqi 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. There was no claim of responsibility by a specific group.
In another possible act of retaliation, hackers claiming to be from Iran breached the website of a little-known US government agency and threatened more cyber attacks.
The website of the Federal Depository Library Program was replaced with a page titled "Iranian Hackers!" that displayed images of Khamenei and the Iranian flag.
"Martyrdom was (Soleimani's)... reward for years of implacable efforts," read a graphic depicting Trump being punched by a first emanating from Iran as missiles fly by.
"This is only (a) small part of Iran's cyber ability !" another caption on the page read in white text on a black background.