WASHINGTON -- The attack that wounded nine people at a mall in the northern US state of Minnesota Saturday night is being investigated as a potential act of terrorism, a US Federal Bureau of Investigation (FBI) official said on Sunday.

"We're currently investigating this as a potential act of terrorism, and I do say potential," Rick Thornton, the special agent in charge of the FBI's Minneapolis Division, told reporters at a press conference Sunday afternoon.

"We don't know whether the suspect was in contact, had connections with, or was inspired by a foreign terrorism organization," he said.

Thornton added that the FBI will look at the suspect's social media accounts, his electronic devices and talk to people associated with him.

The suspect, wearing a private security company uniform, stabbed nine people at a shopping mall in St. Cloud, a city about 70 miles northwest of Minneapolis, Saturday night before being shot dead by an off-duty police officer.

Three of the nine victims remain hospitalized, including one person who is in a life-threatening condition, according to local authorities.

While law enforcement has yet to reveal the name of the suspect, the Amaq News Agency of the Islamic State (IS) group claimed Sunday morning that the suspect was "a soldier of the Islamic State" and carried out the operation in response to the group's calls for attacks in countries that are part of a US-led anti-IS coalition.

The attack happened shortly after an explosion in the Chelsea neighborhood of New York City wounded 29 people. The motivation behind the explosion remains unknown and there's no evidence yet that these incidents were linked.