Monday's attack at Ohio State University was carried out by one of its students, Somali-born Abdul Razak Ali Artan, the authorities said.
The IS-affiliated Amaq news agency called the 18-year-old business undergraduate a "soldier".
Artan drove his car at a group of people, then attacked them with a knife before being shot dead.
Just opportunistic? Analysis by Gordon Corera, BBC Security Correspondent
