ISIS claimed responsibility for Wednesday's attack in Iran that killed more than 80 people who had gathered for a ceremony honoring a top Iranian commander killed in a U.S. drone strike four years ago.

The big picture: It was the deadliest attack in Iran since the 1979 Islamic Revolution and came amid escalating tensions across the region.

• The blasts took place as hundreds gathered at an anniversary ceremony at the cemetery where Gen. Qasem Soleimani, who was the head of the Revolutionary Guard's elite Quds Force, is buried.
• More than 280 people were wounded in the blasts in Soleimani's hometown of Kerman, according to state media.

What to watch: Iranian officials have said Iran's security forces will respond swiftly against those responsible for the attack.

• "Undoubtedly, the perpetrators and masterminds of this cowardly act will soon be identified and brought to justice by the capable security and law enforcement forces," Iranian President Ebrahim Raisi said on Wednesday.

This is a developing story. Please check back for updates.