The Islamic State group says it was behind a car and knife rampage at a US college that left 11 people injured.
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
The IS claim does not prove much in terms of the attack in Ohio. The group often refers to individuals who carry out attacks as its "soldiers", but the crucial question is firstly whether the individual had any form of direct contact with IS.
Face-to-face contact may be unlikely but online communication is possible. If there was no direct contact, it could still be the case that an individual was inspired rather than directed by the group. In this case, an individual may leave his or her own pledge of allegiance in written form or online or in a video.
But until such evidence emerges, it remains hard to know if this is just an opportunistic claim by the group rather than one based on real substance.
Most of the victims were injured by Artan's car, but two were stabbed with a "butcher's knife" and another suffered a fractured skull, officials said.
One of the wounded victims, William Clark, an Ohio State University professor, described how Artan's vehicle had crashed into a large concrete planter before bouncing off and striking him.
"It clipped the back of my right leg and basically flipped me up in the air and I landed on the concrete," he told a news conference.
Mr Clark said Artan then got out of the car and began attacking students before he was shot down.
Surveillance photos showed Artan in the car by himself just before the attack, but investigators are looking into whether anyone else was involved.
Dozens of FBI agents have searched Artan's apartment for clues as to what may have triggered the attacks.
Neighbours described him as polite and said he attended daily prayers at a local mosque.
Artan, who was born in Somalia and was a US permanent resident, arrived in the country in 2014 as the child of a refugee.
He had been living in Pakistan from 2007 to 2014.
Artan recently posted on Facebook about the US treatment of Muslims, according to the AP, citing a law enforcement official who spoke on the condition of anonymity.
"If you want us Muslims to stop carrying lone wolf attacks, then make peace" with the Islamic State group, he allegedly wrote.
Representative Adam Schiff of California, the top Democrat on the House Intelligence Committee, said the act was indicative of someone who may have been self-radicalised.
Militants of the so-called Islamic State have found recruits in the US Somali community in recent years.
About a dozen young men and women from Minnesota's Somali community have travelled to Syria to join militant groups.
Nine men in Minnesota were sentenced on terror charges for plotting to join the Islamic State group.
And a Somali-American man attacked 10 people with a knife at a central Minnesota mall before he was killed by an off-duty police officer in September.
Jaylani Hussein, the executive director of Council of American-Islamic Relations' Minnesota chapter, said some Somali-Americans were concerned about being viewed as "guilty by association".
After Monday's attack, he said: "We must not let the act of one individual, no matter what his motive or background, to further divide our community or our nation."