DUBAI, United Arab Emirates (AP) — Investigators believe suicide bombers likely carried out an attack on a memorial to an Iranian general killed in a U.S. drone strike in 2020, state media reported Thursday, in Iran’s worst mass attack has been struggling for decades and as the wider Middle East remains tense.

A purported statement of responsibility circulating online attributed the attack to the Islamic State group, although this could not immediately be confirmed by The Associated Press.

At least 84 people were killed and another 284 injured in Wednesday’s attack in Kerman. The aim was a ceremony honoring Revolutionary Guard General Qassem Soleimani, held up as an icon by supporters of the country’s theocracy and viewed by the US military as a deadly enemy who helped militants kill American troops in Iraq.

A report by the state news agency IRNA, which was later broadcast on state television, cited an unnamed “informed source” as providing information about the suicide bombing.

The media quoted the official as saying that surveillance footage from the route to the memorial service at Kerman’s Matryrs Cemetery clearly showed a male suicide bomber detonating explosives. The official said the second explosion was “probably” from another suicide bomber, although this could not be determined with certainty.

The alleged Islamic State claim, which was circulated among jihadists online, said the names of the two attackers were Omar al-Mowahed and Seif-Allah al-Mujahid. The claim said the men carried out the attacks wearing explosive vests. Derogatory language was also used when discussing Shiites, whom the Islamic State group considers heretics.

However, the alleged statement did not specify which arm of the Islamic State group carried out the attack, and the group’s name was listed above only in English.

The Islamic State group, which once controlled vast areas of Iraq and Syria, was finally repelled by U.S.-led forces. In the years that followed, disorder reigned, although there were serious attacks.

Islamic State affiliates still exist around the world and the group has claimed responsibility for attacks in Iran in the past. Suicide bombings with high casualties have long been a tactic used by militants.

Iranian state media reports also gave new distances for the blasts to be removed. They described them as occurring 1.5 kilometers (about a mile) and 2.7 kilometers (1.68 miles) from Soleimani’s crypt. The official said the attackers likely chose the locations because they were outside the security area for the memorial service.

An earlier death toll of 103 was revised downward twice after officials discovered that some names had been repeated on a casualty list and because of the severity of wounds suffered by some of the dead, health authorities said. However, many of the wounded were in critical condition, meaning the death toll could rise.

The gathering marked the fourth anniversary of the killing of Soleimani, head of the Revolutionary Guard’s elite Quds Force, in a US drone strike in Iraq. The explosions occurred as long lines of people gathered to mark the event.

Iranian state television and officials described the attacks as bombings without immediately providing clear details about the incident. The attacks came a day after a deputy leader of the Palestinian militant group Hamas was killed in a suspected Israeli attack in Beirut.

Iran has several enemies that could be behind the attack, including exile groups, militant organizations and state actors.

Although Israel has carried out attacks in Iran because of its nuclear program, it has carried out targeted assassinations rather than mass casualty attacks. A US State Department spokesman, Matthew Miller, said American officials had “no reason” to believe Israel was involved in Wednesday’s attack in Iran. This was confirmed by National Security Council spokesman John Kirby at the White House, who said: “Our thoughts are with all the innocent victims and their family members.”

Sunni extremist groups, including the Islamic State group, have carried out large-scale attacks in the past, killing civilians in Shiite-majority Iran, but not in relatively peaceful Kerman.

Iran has also seen mass protests in recent years, including over the death of 22-year-old Mahsa Amini in 2022. The country has also been the target of attacks by exile groups dating back to unrest surrounding the 1979 Islamic Revolution .