Two people were killed and five wounded in a Halloween attack in Quebec City by a sword-wielding suspect dressed in medieval clothing, Canadian police said early Sunday.

The attacks occurred in the historic Old Quebec neighbourhood of the city.

The suspect, "a man in his mid-20s," was armed with a sword and dressed in "medieval clothing," Quebec City police spokesman Etienne Doyon said during a press briefing.

The man, who was not identified, was arrested shortly before 1am and had been "transported to hospital for evaluation," he said.

Police have not given a motive for the attacks.

"It's a man who was dressed medieval. It's a man who carried a sword with him. It's stab wounds - that's all we can tell you at the moment," Doyon said.

The five survivors wounded in the rampage had suffered injuries of varying severity, he said.

Police have asked city residents to stay inside with the doors locked while their investigation was underway.