A Canadian court has sentenced a 29-year-old man to life in prison after he shot dead six worshippers at a Quebec City mosque in 2017.

The attack was the worst ever carried out against the Muslim community in the West.

Alexandre Bissonnette will have to wait 40 years - longer than usual - before he can apply for parole.

In his decision, Judge Francois Huot rejected a prosecution request for a 150-year sentence, which would have been the longest ever in Canada, saying "subjecting a murder to a sentence that exceeds his life expectancy" would be a cruel and unusual punishment under Canadian law.

But he also noted the killer's "visceral hatred of Muslim immigrants".

"You killed six of your compatriots whose only crime was to be different than yourself," Huot said in court.

"With your hatred and racism, you've ruined their lives, yours and your parents', and the crime you've done deserves the greatest denunciation," he said.

A university student at the time of the shooting, Bissonnette appeared to have been seduced by nationalist and supremacist ideologies into committing this "unjustified and deadly" massacre that sought to "undermine our fundamental societal values," the judge said.

The attack at the Quebec Islamic Cultural Centre in the quiet Sainte-Foy neighbourhood of Canada's oldest city, he concluded, will go down in Canadian history "written in blood" as one of this country's worst tragedies.

As the 246-page verdict was read over a six-hour period, Bissonnette sat quietly in the packed courtroom, gazing at his feet while his parents and several friends and family of the victims wiped tears from their eyes.

Outside the courtroom, Aymen Derbali, who was left quadriplegic in the shooting, said he was "very upset and astonished" that Bissonnette did not get more time.

"I had hoped for justice for the victims, for the people who died, and that the sentence reflected the seriousness of the crime," he said.

"This was a very serious attack in a place of worship."