TEHRAN: Iran's supreme leader fought back tears yesterday as a sea of black-clad mourners paid homage to the top commander killed in last week's US drone strike that inflamed tensions across the Middle East. Ayatollah Ali Khamenei choked up as he prayed over the remains of Qasem Soleimani, the slain head of the Revolutionary Guards' Quds Force, at Tehran University. The targeted killing of 62-year-old Soleimani ordered by US President Donald Trump saw Iran vow "severe revenge" before it also took a further step back from the already tattered 2015 nuclear accord with world powers.

In an escalating war of words that has heightened international concern and rattled financial markets, Trump threatened yet more "major retaliation" if Tehran hits back, including strikes on Iranian cultural sites. Writing in all-caps yesterday, Trump tweeted: "IRAN WILL NEVER HAVE A NUCLEAR WEAPON!"

Iraq's parliament has meanwhile demanded the government expel the 5,200 American troops stationed in the country in response to the drone attack in Baghdad which also killed top Iraqi military figure Abu Mahdi Al-Muhandis. Trump has warned a forced departure of US troops would prompt sanctions against Iraq that would "make Iranian sanctions look somewhat tame".

NATO chief Jens Stoltenberg warned Iran must avoid "further violence and provocations" after the alliance held emergency talks on the crisis. "At our meeting today, allies called for restraint and de-escalation. A new conflict would be in no-one's interest," he said. The European Union, whose foreign ministers will hold emergency talks about the crisis Friday, said it was in both Iran and Iraq's interests to "take the path of sobriety and not the path of escalation".

Saudi Arabia - an oil-rich US ally seen as vulnerable to Iranian counter strikes - also appealed for calm after a "very dangerous" escalation. The EU's diplomatic chief Josep Borrell said he "deeply regrets" Iran's latest step back from the nuclear deal. The agreement had offered Tehran relief from sanctions in return for curbs to prevent it acquiring nuclear weapons - but Trump's withdrawal from it in 2018 dramatically weakened the agreement.

Despite its latest step, Iran insisted it will continue to fully cooperate with the UN agency overseeing its atomic program. The European leaders also pleaded with all parties to not jeopardize the ongoing battle against the Islamic State group, which has lost its self-proclaimed "caliphate" but whose militants remain active. Amid the geopolitical tensions in the oil-rich region, crude prices surged and most equities tumbled while the safe-haven commodity gold hit a more than six-year high.

Trump's adviser Kellyanne Conway said yesterday that Trump was still confident he could renegotiate a new nuclear agreement "if Iran wants to start behaving like a normal country". Tehran has said Washington must return to the existing nuclear pact and lift sanctions before any talks can take place.

Trump stood by remarks that cultural sites were potential targets, despite criticism from US politicians that this amounted to a threat to commit war crimes. "They're allowed to kill our people. They're allowed to torture and maim our people. They're allowed to use roadside bombs and blow up our people. And we're not allowed to touch their cultural sites? It doesn't work that way," Trump said.

The raw emotions sparked by the US killing of Soleimani were on full display in Tehran, where mourners formed a sea of black, dotted with red Shiite flags and white signs, in what state television said was a "several million-strong" turnout. "The last time I remember such a crowd was at Ayatollah Khomeini's funeral 30 years ago," said journalist Maziar Khosravi. As they marched down a main artery of the Iranian capital, the mourners chanted "Death to America" and "Death to Israel".

Khamenei's voice cracked and he appeared to weep briefly as he prayed over the flag-draped coffins containing the remains of Soleimani and five other "martyrs" killed in the strike. The supreme leader was flanked by President Hassan Rouhani and other top political and military figures as well as the slain general's replacement as Quds commander, Esmail Qaani. "We must give a crushing response," a 61-year-old named Afkhami said. "We must target whatever military base they have in the region."

Soleimani's daughter Zeinab and the leader of the Palestinian Islamist movement Hamas, Ismail Haniya, also delivered rousing speeches. Zeinab said: "Stupid Trump - a symbol of stupidity and a toy in the hand of Zionism - don't think that with the martyrdom of my father everything is over." The procession made its way to Tehran's Azadi Square, before Soleimani's remains were flown to the holy city of Qom for a ceremony.

A tribute was also paid to Soleimani and Muhandis at a mosque in Baghdad where people trampled on a large portrait of Trump and the US and Israeli flags. In Yemen, hundreds vented their anger over the assassination in a protest called by Tehran-backed Houthi rebels. "We come together with free men around the world to face down the American Satan," an announcer told the crowd in Sanaa's old town. Soleimani was one of Iran's most popular public figures, seen as a hero of the 1980-88 Iran-Iraq war. The general will be laid to rest in his hometown Kerman today, in a martyrs' cemetery next to a war veteran he used to fight alongside with. - Agencies