MONTREAL—Six members of a Trois-Rivieres chapter of the Hells Angels have pleaded guilty to conspiracy to commit murder.

Sentences will range from 10 to 20 years, minus time served since 2009.

The six men were nabbed in during an operation termed SharQc 2009--the acronym for Strategy Hells Angels Region of Quebec--which saw about 150 members of the Quebec biker gang arrested. The arrests were the culmination of more than 80 investigations by the RCMP and Quebec provincial police going back to 1995.

The charges come after 12 members belonging mostly to the Sherbrooke chapter pleaded guilty last year.