Investigators believe suicide bombers probably carried out an attack on a memorial service for an Iranian general killed in a 2020 US drone strike, state media reported on Thursday, as Iran grappled with its worst mass-casualty attack in decades and as the wider Middle East remains on edge.

No-one immediately claimed responsibility for what appeared to be the deadliest militant attack to target Iran since its 1979 Islamic Revolution.

Iran’s leaders vowed to punish those responsible for the blasts, which killed at least 84 people and wounded at least 284.

The explosions struck minutes apart on Wednesday, shaking the city of Kerman, about 510 miles southeast of the capital, Tehran.

The second blast sprayed shrapnel into a screaming crowd fleeing the first explosion.

An earlier death toll of 103 was twice revised lower.

Many of the wounded were in a critical condition, however, so the death toll could rise.

The gathering marked the fourth anniversary of the killing of General Qassem Soleimani, the head of the Revolutionary Guard’s elite Quds Force, in a US drone strike in Iraq.

The explosions occurred near his grave site as queues of people gathered for the event.

Iranian state television and officials described the attacks as bombings, without immediately giving clear details of what happened.

The attacks came a day after a deputy head of the Palestinian militant group Hamas was killed in a suspected Israeli strike in Beirut.

The first bomb on Wednesday was detonated at about 3pm and the other went off some 20 minutes later, the Iranian interior minister, Ahmad Vahidi, told state television.

He said the second blast killed and wounded the most people.

Images and video shared on social media appeared to correspond with the accounts of officials, who said the first blast happened about 700 metres from Mr Soleimani’s grave in the Kerman Martyrs Cemetery near a car park.

The crowd then rushed west along Shohada Street, where the second blast struck about half a mile from the grave.

A delayed second explosion is often used by militants to inflict more casualties by targeting emergency personnel responding to an attack.

Iranian state TV and state-run IRNA news agency quoted emergency officials for the casualty figures.

Authorities said Thursday would be a national day of mourning.

Iran’s Supreme Leader Ayatollah Ali Khamenei said the attackers will face “a harsh response”, though he did not name any possible suspect.

Iranian President Ebrahim Raisi said: “Undoubtedly, the perpetrators and leaders of this cowardly act will soon be identified and punished.”

Iran has multiple foes who could be behind the assault, including exile groups, militant organisations and state actors.

While Israel has carried out attacks in Iran over its nuclear programme, it has conducted targeted assassinations, not mass casualty bombings.

A US State Department spokesman, Matthew Miller, said American officials had “no reason” to believe Israel was involved in Wednesday’s attack in Iran.

That was echoed by National Security Council spokesman John Kirby at the White House, who said “our hearts go out to all the innocent victims and their family members”.

Sunni extremist groups including the so-called Islamic State terrorist group have conducted large-scale attacks in the past that killed civilians in Shiite-majority Iran, though not in relatively peaceful Kerman.

Iran also has seen mass protests in recent years, including those over the death of 22-year-old Mahsa Amini in 2022.

The country has also been targeted by exile groups in attacks dating back to the turmoil surrounding its 1979 Islamic Revolution.

Iran itself has been arming militant groups over the decades, including Hamas, the Lebanese Shiite militia Hezbollah and Yemen’s Houthi rebels.

As Israel wages its devastating war in Gaza after Hamas’s October 7 attacks that killed 1,200 people, both Hezbollah and the Houthis have launched attacks targeting Israel that they say come on behalf of the Palestinians.

Israel is suspected of launching the attack on Tuesday that killed a deputy head of Hamas in Beirut, but that attack caused limited casualties in a densely populated neighbourhood of the Lebanese capital.

Last week, a suspected Israeli strike killed a Revolutionary Guard commander in Syria.

A Houthi spokesman, Mohammed Abdel-Salam, sought to link the bombings to Iran’s “support for the resistance forces in Palestine and Lebanon”, though he did not specifically blame anyone for the attack.

Some Iranian officials also hinted at Israeli and American involvement without offering evidence, which is common after militant attacks.

In Beirut, Hezbollah leader Hassan Nasrallah called the people who died in the attacks “martyrs who died on the same road, cause and battle that was led by” Mr Soleimani.

The government of neighbouring Iraq expressed condolences to the victims, and the European Union issued a statement offering “its solidarity with the Iranian people”.

Even Saudi Arabia, a longtime regional rival which reached a detente with Iran last year, offered its sympathies.

Mr Soleimani was the architect of Iran’s regional military activities and is hailed as a national icon among supporters of Iran’s theocracy.

He also helped secure Syrian President Bashar Assad’s government after the 2011 Arab Spring protests against him turned into a civil, and later a regional, war that still rages today.

Mr Soleimani had been relatively unknown in Iran until the 2003 US invasion of Iraq. His popularity and mystique grew after American officials called for his killing over his help in arming militants with penetrating roadside bombs that killed and maimed US troops.

A decade and a half later, Mr Soleimani had become Iran’s most recognisable battlefield commander. He ignored calls to enter politics but grew as powerful, if not more so, than its civilian leadership.

Ultimately, a drone strike launched by former US president Donald Trump’s administration killed the general, part of escalating incidents that followed America’s 2018 unilateral withdrawal from Tehran’s nuclear deal with world powers.

Mr Soleimani’s death has drawn large processions in the past.

At his funeral in 2020, a stampede broke out in Kerman and at least 56 people were killed and more than 200 were injured as thousands thronged the procession.

Until Wednesday, the deadliest attack to strike Iran since the revolution was the 1981 truck bombing of the Islamic Republican Party’s headquarters in Tehran.

That attack killed at least 72 people, including the party’s leader, four government ministers, eight deputy ministers and 23 parliament members.

In 1978, just ahead of the revolution, an arson attack at the Cinema Rex in Abadan killed hundreds of people.