The man, who was wearing a private security uniform, made references to Allah and asked at least one person if they were Muslim before he assaulted them at the Crossroads Center mall in St. Cloud on Saturday, the city's Police Chief William Blair Anderson told reporters.

Authorities declined to identify the suspect, who was killed by an off-duty policeman, because the investigation is underway.

The Federal Bureau of Investigation considers the episode a "potential act of terrorism," Richard Thornton, FBI special agent in charge of the agency's Minneapolis division, said at a news conference.

He said the investigation is in its early stages and it was not known if the man had discussed his plan of attack with others.

Authorities had said earlier there were eight stabbing victims. One injured person transported himself to a hospital and was not initially counted, St. Cloud Mayor Dave Kleis said at the news conference.

Three victims remained hospitalized as of Sunday but none had life-threatening injuries, Kleis said.

Kleis said Jason Falconer, the off-duty officer from the Avon Police Department, a jurisdiction outside of St. Cloud, "clearly prevented additional injuries and loss of life" by shooting the man.

Amaq, the news agency affiliated with the Middle Eastern extremist group Islamic State, issued a statement on Sunday saying, "The executor of the stabbing attacks in Minnesota yesterday was a soldier of the Islamic State and carried out the operation in response to calls to target the citizens of countries belonging to the crusader coalition."

Reuters was not immediately able to verify the Amaq claim.

The knife attack in St. Cloud, a community about 60 miles (100 km) northwest of Minneapolis-St. Paul, came at a time of heightened concern in the United States about the threat of violence in public places.

An explosion rocked New York City's bustling Chelsea district on Saturday, injuring 29 people in what authorities described as a deliberate criminal act. But both New York Governor Andrew Cuomo and New York City Mayor Bill de Blasio said there was no indication it was linked to international terrorism.

A pipe bomb also exploded in a New Jersey beach town on Saturday along the route of a charity race to benefit military veterans but no injuries were reported in what investigators also were treating as a possible act of terrorism.

Democratic presidential nominee Hillary Clinton said she strongly condemned "the apparent terrorist attacks in Minnesota, New Jersey, and New York" and said Islamic State's claim of responsibility for the St. Cloud attack should "steel our resolve to protect our country and defeat ISIS and other terrorist groups."

Investigators are looking for possible connections among the Saturday attacks but so far have not found any links.

In St. Cloud, the attacker entered the mall in the evening as it was busy with shoppers, Anderson said. He attacked his victims at several sites in the shopping center, which will remained closed on Sunday as police investigate, the police chief said.

The victims were male and female, Kleis said, and ranged in age from mid-50s to a 15-year-old female.

Police officials said they were still interviewing witnesses hours after the attack.