Here’s what’s known — and what remains unclear — about Wednesday’s deadly explosions in Iran:

• Authorities say the twin bombings killed at least 103 people and wounded 211 others.

• The attack is the deadliest to strike Iran since its 1979 Islamic Revolution.

• The second explosion occurred about 20 minutes after the first, which is often a technique used by militants to harm both civilians and emergency responders after an initial assault.

• The attack came during commemorations for the fourth anniversary of the killing of Gen. Qassem Soleimani, the head of the Revolutionary Guard’s elite Quds Force, in a U.S. drone strike in neighboring Iraq. The explosions occurred near his grave site as long lines of people gathered for the event.

• No group has claimed responsibility for the attack in Kerman.

• Iran has faced targeted killings and sabotage attacks suspected to have been carried out by Israel. However, those assaults did not include mass casualty bombings like Wednesday’s attack.

• Sunni extremist groups including the Islamic State group have conducted large-scale attacks in the past that killed civilians in Shiite-majority Iran.

This is terrorism written all over it. 

US Says Israel Not Behind Iran Blast, Warns Against Escalation

"The United States was not involved in any way, and any suggestion to the contrary is ridiculous," State Department spokesman Matthew Miller said of Wednesday's violence.

"We have no reason to believe that Israel was involved in this explosion," he said.

"We do express our sympathies to the victims and their loved ones who died in this horrific explosion," he said.

"It is in no one's interest -- not in the interest of any country in the region, not in the interest of any country in the world -- to see this conflict escalated any further than it already is," he said.

Miller declined to assess who carried out the attack in Iran.

US Says Israel Not Behind Iran Blast, Warns Against Escalation | Barron's (barrons.com)