A Somali-born refugee has been arrested in connection with attacks in Edmonton, Alberta in which five people were injured, officials say.

The unnamed 30-year-old man is suspected of stabbing a policeman and injuring four pedestrians on Saturday. The officer was controlling traffic at a Canadian Football League game when he was struck by a car at high speed and then attacked with a knife.

Prime Minister Justin Trudeau has called it a “terrorist attack”.

Edmonton officials say the suspect could face terror and murder-related charges. They add that he had been known to police for believing in extremist ideology.

According to broadcasters CBC and CTV, a flag belonging to so-called Islamic State was found inside the vehicle that hit the police officer.

The officer and his vehicle were rammed by a car outside Alberta’s Commonwealth Stadium on Saturday evening. The driver then stabbed the uniformed officer several times, before fleeing on foot.

Shortly before midnight, a man driving a rented van was pulled over at a checkpoint. His name on documents was said to be “very similar” to that of the man police were searching for. The truck then fled the scene, and was pursued by officers. Four pedestrians were struck during the chase in what police say appeared to be a deliberate action.

Two injured pedestrians have since been released from hospital and the police officer is recovering from his wounds.

Mr Trudeau said he was both “deeply concerned and outraged” by “this senseless act of violence”. Edmonton Mayor Don Iveson urged calm. “Terrorism is about creating panic and sowing divide about disrupting people’s lives,” he said. “We can succumb to that or rise above it.”