TEHRAN -- The Islamic State (IS) terrorist group on Thursday claimed responsibility for two deadly bomb blasts in the southeastern Iranian city of Kerman.

The IS released a statement saying two of its suicide bombers had used explosive belts in two "operations," according to Iran's official news agency IRNA.

At least 84 people were killed and 284 others injured on Wednesday in the twin bombing near the tomb of top Iranian general Qassem Soleimani in Kerman while there was a crowded gathering to mark the fourth anniversary of Soleimani's death in a US drone strike.

Earlier, IRNA citing an informed source reported that surveillance camera footage and other evidence around the first blast pointed to a suicidal attack. The second blast, still under probe, was "most probably" also a suicide attack, said the source.

The first blast was about 700 meters from the tomb and the second was a kilometer away. Rahman Jalali, the deputy governor of Kerman province for political and security affairs, told the agency the explosions were carried out by "terrorists," according to IRNA.

Iran's Supreme Leader Ali Khamenei vowed on Wednesday in a statement that a "harsh response" would be given to those who perpetrated and ordered the deadly "act of terror."

Soleimani, one of the most powerful military commanders in Iran, was killed on Jan 3, 2020, near Baghdad's international airport in a drone strike ordered by then-US President Donald Trump.

He was buried in his hometown of Kerman after a funeral that drew millions of mourners across Iran. Iran denounced the assassination as "state terrorism" and vowed revenge.