Mounties say the man accused of attacking a police officer and running down four pedestrians with a rental truck in a dramatic late-night downtown chase is a Somali refugee once investigated for espousing extremism.

RCMP assistant commissioner Marlin Degrand said the suspect, 30, was checked thoroughly in 2015 and deemed at that time to not pose a threat.

"There was insufficient evidence to pursue terrorism charges or a peace bond," Degrand said Sunday. "The suspect was actually not deemed at that time to pose a threat to the security of Canada."

Degrand said files on the suspect were kept and shared with other intelligence and police agencies after 2015, but said that was as much as the law would allow.

"We didn't have sufficient evidence to warrant continued investigation of that individual following the 2015 (check)," he said.

Police did not name the suspect, who they said was arrested with an Islamic state flag in one of his vehicles.

Degrand initially said was the suspect was the process of making a refugee claim in Canada, but a spokesman with the federal Public Safety Department later clarified that he had already been found to be a refugee by the Immigration and Refugee Board.

He is facing a number of charges, including five counts of attempted murder, dangerous driving and participation in a terrorist activity.

Edmonton Police Chief Rod Knecht said, so far, it appears the suspect does not have any co-conspirators.

"From all indications it appears that this was a single individual acting alone," said Knecht. "We have no reason to believe that there is any threat to our city."

The attacks began around 8:15 Saturday night near Commonwealth Stadium, just north of downtown, during a game between the CFL's Edmonton Eskimos and Winnipeg Blue Bombers. It was military appreciation night. Canada's chief of defence staff, Gen. Jonathan Vance, conducted the pregame coin flip and two CF-18 fighter jets did a fly-past before kickoff.

Outside the stadium, Edmonton police Const. Mike Chernyk, with his marked, flashing cruiser was handling crowd control and security when a speeding white Chevy Malibu rammed through a barrier and hit his car, sending him flying five metres through the air.

The driver then got out, pulled out a large knife and began stabbing him. Knecht said Chernyk, a 10-year-veteran, fought back, forcing the suspect to flee on foot.

"He was in a struggle for his life, holding onto his gun with one hand and blocking the knife with his other," said Knecht. "It's a testament to his experience and training that he survived."

Knecht said Chernyk has since been released from hospital and is expected to make a full recovery.

"He has stab wounds on his face and head from the knife and significant abrasions on his arms as a result of being hit by the car."

Chernyk managed to radio in what had happened and the manhunt was on.

Police set up checkpoints and began stopping cars, leading to a second encounter hours later with the suspect, now driving a U-haul cube van, east of the stadium just after midnight.

Knecht said when the U-haul pulled over for the checkpoint, the driver produced identification linking him to the registered owner of the Malibu.

He became suspicious when police held him up, and decided to flee. The U-Haul then sped off toward Jasper Avenue, downtown Edmonton's main east-west thoroughfare, with multiple police cars in pursuit.

Knecht said the suspect drove in the opposite lane, almost T-boned a vehicle and purposely drove into pedestrians, injuring four.

He said the call was made to keep the high-speed pursuit through the downtown, busy with late night bar and night-club goers, because of the threat posed by the suspect.

Of the four pedestrians, two suffered head injuries including a skull fracture. Two have been released from hospital.

"Their injuries range from broken bones to brain bleeds," said Knecht.

He said officers used a "tactical manoeuvre" to force the truck to crash onto its side just south of Jasper Avenue. Officers smashed through the windshield and tossed in a stun grenade to distract the driver. When he resisted, they used a stun gun to make the arrest.

"No shots were fired. In fact, no shots were fired anywhere in this entire incident," said Knecht.

Austin Elgie, manager of The Pint bar, saw the van zoom by with police giving chase.

The van "peeled" into an alley where people were smoking, he said.

"There were like 10 cop cars following him ... It was crazy. It just came around the corner, ripping. I thought at first he was pulling over for the cops coming by, but he was clearly the one they were chasing."

Alberta Premier Rachel Notley called the attacks horrific.

"Hatred has no place in Alberta. It's not who we are," Notley said Sunday.

Prime Minister Justin Trudeau also condemned the violent events as a "terrorist attack" and a "senseless act of violence."

"We cannot -- and will not -- let violent extremism take root in our communities," he said.

In the United States, President Donald Trump's press secretary issued a statement saying "Law enforcement authorities from the United States are in touch with their Canadian counterparts to offer assistance with the ongoing investigation."

Edmonton Mayor Don Iveson urged calm and compassion.

"It is vital now that we not succumb to hatred, that we not be intimidated by violence," said Iveson. "Terrorism is about creating panic and about sowing divide and about disrupting people's lives.

"We can succumb to that or we can rise above it."

-- With files from Jennifer Graham in Regina and Andy Blatchford in Ottawa

"Our thoughts are with Γåòedmontonpolice member injured on duty tonight & hoping for a speedy recovery," she wrote. "Grateful for our first responders."