Crown prosecutors are appealing the sentence given last month to Quebec City mosque shooter Alexandre Bissonnette.

In court documents filed just hours before the appeal deadline expired, the Crown says Bissonnette's life sentence, with no chance of parole for 40 years, is too lenient.

A Quebec Superior Court judge altered part of the Criminal Code he found unconstitutional when he sentenced Bissonnette in February.

It is one of the longest sentenced ever handed down in Canadian history. Crown lawyers initially sought a life sentence with no chance of parole for 150 years. They now want parole to be an option after 50 years.

The Crown's notice of appeal accuses the trial judge of minimizing the horror of Bissonnette's actions by saying "just two minutes of his life was enough to turn him into an assassin."

Bissonnette, the Crown said, had planned the attack on the mosque well in advance. The 40-year sentence, they added, doesn't reflect the "gravity of the infraction and [Bissonnette's] degree of responsibility."

Bissonnette, 29, pleaded guilty last year to killing six people, and attempting to kill dozens of others, at the Quebec City Islamic Cultural Centre in 2017.

His lawyers appealed the sentence last week, claiming it is too harsh. They want Bissonnette to be eligible for parole after 25 years.