Edmonton attack
A rental truck lies on its side in Edmonton, Canada, on October 1, 2017, after a high speed chase. Canadian police arrested a man early Sunday suspected of stabbing an officer and injuring four pedestrians in a series of violent incidents being investigated as an 'act of terrorism.' The crime spree began late September 30 outside a football stadium and ended hours later with a high speed chase in which the driver of the rented truck plowed into pedestrians, police said MICHAEL MUKAI/AFP/Getty Images

A Somali asylum seeker suspected of being behind knife and vehicle terrorist attacks in Edmonton, Canada, was investigated by police for "espousing extremist ideology" in 2015.

The suspect was arrested hours after he struck a police officer with a vehicle outside Alberta's Commonwealth Stadium and repeatedly stabbed him before fleeing the scene on foot on 1 October.

Just before midnight, a man driving a rented van was pulled over at a checkpoint. Authorities said the man's name was reportedly "very similar" to that of the suspect police were looking for.

The man fled the scene and rammed his van into a crowd, injuring four pedestrians during the chase, in what authorities said was a deliberate action.

Although police have not yet confirmed the identity of the suspect as he has not been formally charged, CBC News and CTV News identified him as 30-year-old Abdulahi Sharif. Pending charges include terrorism and five counts of attempted murder.

Police said the suspect had been known to authorities since 2015, when he was investigated as he was "espousing extremist ideology."

"At the end of that exhaustive investigation, there was insufficient evidence to pursue terrorism charges or a peace bond," said Marlin Degrand, assistant commissioner at the Royal Canadian Mounted Police (RCMP), according to CTV News.

RCMP said in a statement on Twitter that police "are confident the 2015 allegations were investigated to the fullest. RCMP continuing to work with partners and tools to prevent violent extremists from committing a terrorism offence."

Police believe the suspect acted alone, but investigation into the incidents continues. The reported recovery of a flag belonging to the Islamic State (Isis) terror group inside the vehicle that hit the police officer led to suspicions the attacker could be an Isis sympathiser.

Members of the Somali community in Edmonton told BCB News the suspect kept a low profile.

A former co-worker described him as a "very strange [man]. He would rant. It was very incoherent. He would just bounce from idea to idea, tangent to tangent, just about what he believed in and he definitely had genocidal beliefs, you could say.

"He had major issues with polytheists, he said they need to die. That sort of thing. I only had a handful of conversations with him about it; those only occurred when there were just two of us in the work room."

Prime Minister Justin Trudeau called the incident a "terrorist attack" adding he was "deeply concerned and outraged" by "this senseless act of violence".