Ottawa (AFP) - A Somali refugee who attacked a policeman with a knife after striking him with his car and then injured four others in a driving rampage in Edmonton, Alberta was charged with five counts of attempted murder Monday.

No terrorism charges were announced, but "we're still very much in the infancy stage" of the investigation, Royal Canadian Mounted Police Superintendent Stacey Talbot told a press conference.

"The complexities of a terrorism investigation are vast. If warranted, further charges will be pursued," she added.

Abdulahi Hasan Sharif, a 30-year-old refugee from Somalia, is scheduled to appear in an Edmonton court on Tuesday morning where he will be formally charged with 11 counts including attempted murder, dangerous driving, flight causing bodily harm and possession of a weapon for dangerous purposes.

According to Canadian media, he arrived in Canada in 2012. His work permit, however, expired at the end of May.

On Sunday, Prime Minister Justin Trudeau denounced what he said had been a "terrorist attack" in Edmonton, the capital of Canada's oil-rich Alberta province.

The RCMP antiterrorism squad, meanwhile, took over the investigation after an Islamic State group flag was discovered in the accused's car.

Late Saturday, the suspect drove his car into a barrier outside a football stadium and struck a policeman directing traffic. He then jumped out and tried to stab the officer, who fought him off with one hand.

Hours later, the suspect took police on a wild chase through the city's downtown in a rented van as he tried to mow down pedestrians, before the vehicle was knocked over and the driver was apprehended.

Two of the four pedestrians whose injuries, according to Edmonton police chief Rod Knecht, had ranged from "broken arms to brain bleeds," have been released from hospital, authorities said Monday.

Edmonton Police Constable Mike Chernyk, 48, is also out of hospital.