Eight wounded, suspect killed in Minnesota attack claimed by IS

Minnesota police said on Sunday they were investigating a shopping mall stabbing spree that wounded eight late the previous night, but could not comment on a claim that the Islamic State (IS) group was behind the attack.

Meanwhile, two other attacks carried out in the US on the same day - a New York bombing and a New Jersey pipe bomb blast - were under investigation on Sunday for potential terror links.

Local officials had no immediate response to a claim by the IS-linked news agency Amaq that the Minnesota assailant was "a soldier of the Islamic State".

A man who made "some references to Allah" stabbed and injured eight people in a shopping mall in the city of St Cloud late Saturday before he was shot dead by an off-duty officer, police said.

The suspect "asked at least one person if they were Muslim before he assaulted them," Blair Anderson, the St Cloud police chief, told journalists.

But he emphasised that the assailant's motivation remained unclear.

"Whether that was a terrorist attack or not, I'm not willing to say that right now because we just don't know," he said.

Authorities say there is no evidence that any of the attacks were coordinated, but the timing in less than 24 hours raises fears about security - already a hot button issue in the country's deeply divisive presidential election between Hillary Clinton and Donald Trump.

Twenty-nine people were injured when a bomb exploded in New York's upmarket Chelsea neighbourhood on Saturday night, damaging neighbouring buildings, shattering glass and sending shrapnel flying across the street.

A second bomb was uncovered by police four blocks away and defused safely, before undergoing analysis.

Hours earlier, less than 160km south in New Jersey, a pipe bomb exploded in a trash can on the sidelines of a Marine Corps run, causing no injuries but forcing the cancellation of the race.

A St Cloud police officer told AFP on Sunday that the department was actively investigating the stabbing attacks, but had no further information for public release and had no immediate plans for further news briefings.

Speaking shortly after midnight, Chief Anderson said the armed suspect entered the Crossroads Center mall in St Cloud - a city of about 67,000 people some 110 km northwest of Minneapolis - and attacked at least eight people.

The lone suspect was wearing a private security uniform and had at least one knife, and "made some references to Allah," the police chief said.

"That suspect was confronted by an off-duty police officer and summarily shot and killed," he said.

Anderson said the eight wounded people were taken to a hospital. All but one was later released.

The FBI is investigating the stabbing spree as a "potential act of terrorism," the agent in charge said on Sunday.

Agent Rick Thornton told journalists in the city of St Cloud that there was still "a lot we don't know" about any possible international link to the assailant.

The suspect had a history of minor traffic violations, Anderson said, adding that police do not currently believe the attack was connected to any other incident.

Democratic presidential candidate Hillary Clinton said she had been briefed about the Minnesota stabbing and Saturday's explosions in New York, as well as a pipe bomb blast hours earlier in a trash can in New Jersey in which no one was injured.

The St Cloud mall will remain closed as police continue their investigation.

"It's an awful day," Anderson said. "Starting tomorrow things won't be the same here."