MONTREAL -- Police arrested 12 protesters, all under the age of 18, who had glued their hands to the window of a downtown shop on Friday evening, in an effort to spread a message of environmentalism. 

Earlier, about 40 members of Extinction Rebellion had gathered to protest the annual shopping frenzy that is Black Friday.

They carried posters criticizing the cost of consumerism and how damaging it is to the planet.

"Black Friday kills," read one of their banners.

The protesters rallied outside the Best Buy on Sainte-Catherine Street just before the store opened its doors to about 100 shoppers at 6 a.m. and continued protesting at various area stores throughout the day. Protesters on Friday evening blocked Saint-Catherine St. near Peel St., chanting and hoisting signs.

They also hosted a clothing giveaway.

"It's black Friday," said Marouane Joundi, a spokesperson for La planète s'invite à l'université who was protesting on Montreal streets. "We're here to make our own version of it: green Friday. We're here to raise awareness of the ecological and social impact of mass consumption in the current context of absolute climate emergency."

Similar demonstrations went on in Quebec City.

Many stores are also offering Black Friday sales online, which will go until Cyber Monday. 

Correction:

Due to a translation error, an earlier version of this article said the 12 people had been arrested for linking hands, blocking access to a shop. In fact, the protesters glued their hands to a shop window.