Black-clad mourners packed Iran's second city Mashhad on Sunday as the remains of top general Qasem Soleimani were paraded through the streets after he was killed in a US strike. "Iran's wearing black, revenge, revenge," they chanted as darkness fell and they followed a truck carrying Soleimani's coffin towards the floodlit Imam Reza shrine. The mourners threw scarves onto the roof of the truck so that they could be blessed by the "blood of the martyr". Soleimani, who spearheaded Iran's Middle East operations as commander of the Revolutionary Guards' Quds Force, was killed in a US drone strike Friday near Baghdad airport. He was 62. The attack was ordered by President Donald Trump, who said the Quds commander had been planning an "imminent" attack on US diplomats and forces in Iraq. Soleimani's remains had been returned before dawn to the southwestern city of Ahvaz, where the air resonated with Shiite chants and shouts of "Death to America" during a procession. People held aloft portraits of Soleimani, one of the country's most popular public figures who is seen as a hero of the 1980-88 Iran-Iraq war. The "million-man" turnout in Mashhad, northeastern Iran, forced the cancellation of a Sunday night ceremony in Tehran, said the Islamic Revolutionary Guard Corps who urged citizens instead to attend a memorial Monday at Tehran University. In the face of growing Iraqi anger over the strike, the country's parliament Sunday urged the government 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. Late Saturday Trump warned on Twitter that the United States would target 52 sites "important to Iran & Iranian culture" and hit them "very fast and very hard" if American personnel or assets were attacked. - 'Terrorist in a suit' - Iranian Foreign Minister Mohammad Javad Zarif tweeted that "targeting cultural sites is a WAR CRIME". Former Guards chief Mohsen Rezai went further, threatening to turn the Israeli cities of Haifa and Tel Aviv "to dust" if Trump carried out his threat. "I doubt they have the courage to initiate" a conflict, said Major General Abdolrahim Mousavi. Iran's communications minister, Mohammad Javad Jahromi, branded Trump a "terrorist in a suit" in a Twitter post. Khamenei's military adviser, Brigadier General Hossein Dehghan, told CNN that Iran's response to the assassination "for sure will be military and against military sites". US Secretary of State Mike Pompeo admitted there was a "real likelihood" of an Iranian attack on US soldiers, warning however "it would be a big mistake". Calling Iran a "kleptocratic regime", Pompeo said the US would not hesitate to hit Iran hard if it came under attack. In Lebanon, Hassan Nasrallah, the head of the Iran-backed Hezbollah movement, insisted the "price" for Soleimani's killing would be attacks on "US military bases, US warships, each and every officer and soldier in the region". British Prime Minister Boris Johnson said his country, a key US ally, "will not lament" Soleimani's death. But he agreed in talks with the leaders of France and Germany to work together towards reducing tensions in the Middle East, a German government spokesman said. "Iran in particular is urged to exercise restraint in the current situation," the spokesman said, adding that the leaders agreed that de-escalation "is now urgent". 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. A year on, Iran began hitting back by reducing its nuclear commitments with a series of steps every 60 days, the most recent deadline passing on Saturday. Foreign ministry spokesman Abbas Mousavi said Tehran would finalise the fifth step in a meeting on Sunday night, noting the nature of its move was altered by Soleimani's killing. Later in the evening, the government announced in a statement that Iran would forego the "limit on the number of centrifuges", adding however Tehran would continue cooperating with the UN nuclear watchdog. - Cyber attack - In Tehran, deputies chanted "Death to America" for a few minutes during a regular session of parliament. "Trump, this is the voice of the Iranian nation, listen," said speaker Ali Larijani. 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, semi-official news agency 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 strike. Soleimani's remains are to be flown to the capital, where Khamenei is due to pray over them at Tehran University on Monday before being taken to the holy city of Qom for a ceremony at Masumeh shrine, ahead of a funeral Tuesday in his hometown Kerman. 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.