ISIS claimed responsibility for a pair of Wednesday attacks in Tehran in which suicide bombers and teams of gunmen stormed Iran's parliament and the nearby shrine of Ayatollah Ruhollah Khomeini, killing at least 12 and injuring dozens of others.

This is the first attack orchestrated by ISIS in the Islamic Republic, SITE Intel Group reported. It wasn't initially clear if the death count, reported by state broadcaster IRIB, included the attackers.

In a rare and stunning move, ISIS released video from inside the parliament building while the attack was under way.  The video, circulated online, shows a gunman and a bloody, lifeless body of a man lying on the ground next to a desk. A voice on the video praises God and says in Arabic: "Do you think we will leave? We will remain, God willing." Another voice repeats the same words. The two appeared to be parroting a slogan used by IS spokesman Abu Mohammad al-Adnani, who was killed in Syria last year.

The parliament assault ended Wednesday morning with all four attackers there being killed.