One of the two explosions that ripped through a crowded area in southeastern Iran's city of Kerman on Wednesday was a suicide blast, state media said on Thursday.
Citing "a well-informed source" in the city, state news agency IRNA said the first explosion was a "suicide attack."
At least 84 people died in the two blasts outside the cemetery where thousands of people had gathered to commemorate the fourth anniversary of the death of top military commander Gen. Qassem Soleimani.
Earlier, authorities had put the death toll at 103, which was later revised by forensic experts to 84, besides 284 injured.
Soleimani, the former head of the Islamic Revolution Guard Corps (IRGC) Quds Force, was killed in a US drone strike outside the Baghdad International Airport in January 2020.
IRNA cited the source as saying that the preliminary investigation indicated the bombings were caused by explosive devices but after the examination of evidence, including CCTV footage, it became certain that the first explosion was a suicide attack.
The other explosion was "probably the same" but the investigation continues, the report added, citing the unidentified source.
The first suicide bomber was a man who was "torn into pieces as a result of the explosion" and efforts to establish his identity are underway, the report stated, noting that the two bombings took place 1.5 km and 2.7 km away respectively from the grave of Soleimani.
The reason why the perpetrators chose that particular area, it said, was "due to the impossibility of passing through the inspection gates."
Meanwhile, the Daesh terror group, in a statement on its Telegram channel, claimed responsibility for the attacks.
The group said "more than 300" were killed in two suicide bombings in the Iranian city, identifying the two bombers as Omer al-Mohed and Safiullah Mujahid who detonated their explosive-laden vests in the crowd.
The attacks in Kerman are the deadliest since the 1979 revolution in terms of the number of casualties.
In a tweet on Wednesday, the Iranian president's close aide and deputy chief of staff Mohammad Jamshidi said the responsibility for it "lies with the US and the Zionist regime (Israel)."
Earlier, President Ebrahim Raeisi and Interior Minister Ahmad Vahidi also hinted at the involvement of Israel and the US, though without making any direct inferences.
