Thousands of protesters outraged by two laws passed Friday to tamp down civil unrest marched through downtown Montreal on Saturday night, many of them wearing now-illegal masks or hoods.

Authorities declared the protest illegal about a half-hour after it began at 8:30 p.m. ET. Then, a little after 11 p.m., Montreal police ordered protesters to disperse and called in the provincial police force's riot squad.

The night ended with 69 arrests, police said.

Police fired tear gas at demonstrators in at least three areas of the city: near McGill University's campus, at the intersection of St. Laurent Boulevard and Ontario Street, and in a park near the Université du Québec à Montréal.

Montreal police spokesman Ian Lafrenière said a "hard core" of protesters was engaging in illegal acts, including a few who were throwing beer bottles at constables.

Student protesters were joined by others spilling out of bars and clubs.

Some people from both groups built fires from traffic cones and construction materials, cheering as the flames lit up the streets and sent plumes of black smoke billowing into the night sky.

Riot police gather near a fire during the demonstration in Montreal on Saturday. (Graham Hughes/Canadian Press)

Some protesters also complained of police violence. On St. Denis Street, a line of riot officers charged a gathering of people and started beating a man in his 50s or 60s who was retreating, but not nimbly enough to avoid them. A demonstrator told TV cameras that an officer shoved him with a bicycle, while elsewhere riot-squad units charged at peaceful street rallies.

"I'm drunk! I've been on a patio all evening!" one young, handcuffed woman told police, in an exchange caught on the live broadcast of Concordia University Television (CUTV).

Riot police repeatedly warned protesters they would be incarcerated throughout the weekend unless they dispersed.

Estimates varied widely on the number of people in the streets, with numbers ranging from 3,000 at the beginning of the first march to 20,000 at the demonstrations' peak, when packs of protesters split up to locations around the downtown.

Protest spreads to Saturday Night Live

The protest has spread beyond Canada's borders.

In New York, members of the Montreal-based rock band Arcade Fire wore the movement's iconic red squares during an appearance with The Rolling Stones' Mick Jagger on Saturday Night Live. Jagger wore a red shirt, but no red square.

A day earlier, players in Quebec's film industry were sporting them at the Cannes Film Festival.

Online, the website for the Quebec Liberal Party and the province's Education Ministry were down for most of Saturday in an apparent cyber attack.

While no one claimed responsibility, the hacker group Anonymous has taken an interest. The group wrote on Twitter that Bill 78 "must die" and later issued a video denouncing the law.

Bill 78 lays out strict regulations governing demonstrations of over 50 people, including having to give eight hours' notice for details such as the protest route, the duration and the time at which they're being held.

Fines up to $125,000

The night rally was the 26th in a row in the city, part of a province-wide surge of civil disobedience that began as a denunciation by striking students of the Liberal government's plan to hike tuition fees and has grown to encompass a wide array of social causes.

The most recent cause for complaint is the adoption of emergency legislation to try to end the escalating crisis.

On Friday, the Quebec government passed Bill 78, which comes with heavy financial penalties for violations.

The law:

Suspends winter semesters at schools where students have boycotted classes.

Stipulates penalties for groups who try to block access to schools, and even for organizations that don't induce their members not to.

Requires any public protest of more than 50 people to alert police at least eight hours ahead of time, with the event's start time, route and date. Groups that violate the law face fines of up to $125,000.

The City of Montreal passed its own measures on Friday, making it illegal to wear a mask, scarf or hood during a public protests.

'Draconian' anti-protest measure

Legal experts, civil-rights groups, unions and student groups have blasted the hardline Bill 78. A full-page newspaper advertisement paid for by the Quebec government to explain the law was flanked by other ads from civil society groups alarmed by what they call "draconian" measures to contain the tuition hike crisis.

One of Quebec's teachers' unions, FAE, placed an ad with Premier Jean Charest's face and a headline that says "shame has a face."

"We don't have that many means to express our indignation," FAE president Pierre Saint-Germain said in an interview with CBC's French-language service on Saturday.

"I'll tell you, frankly, that with this bludgeon law, it's becoming harder and harder for people and organizations, from students to unions, to express themselves publicly."

Montreal newspaper Le Devoir published an editorial titled "Abuse of power" and called on the Liberal government to seek mediation in the ongoing student protest.

Constitutional lawyer Julius Grey called Bill 78 a "terrible law" that suspends the freedom to association, express and protest, without sufficient reason.

"What I note in this law is that there is no opening for discussion — what kind of education we want to have, is higher education a question of preparing for the job market, or a more academic question, to promote learning? There is none of that.

"This is simply an attempt to end a debate, to appear strong and determined."

Others who spoke out include former Quebec Superior Court judge John Gomery.

Court challenge

The province's two main umbrella student groups, the Fédération étudiante collégiale du Québec and the Fédération étudiante universitaire du Québec, said Saturday they will launch a legal challenge of Bill 78 this week.

Vocal denunciations of the planned tuition increases began in March 2011, but it was only in February that they ramped up into a student strike that at its peak saw 180,000 pupils boycotting college and university classes. Since then, large regular protests have touched Montreal, Quebec City, Gatineau, Trois-Rivières and other towns.

The government wants to raise university fees by more than 70 per cent over the next five years, to $3,800 annually. The province points out that that would still be among the lowest tuition rates in the country. Opposing students say it will render even more of them indebted on graduation and put higher education financially out of reach for more people.

Negotiations have largely been at an impasse. On Monday, Line Beauchamp cited the crisis in resigning from her cabinet post as education minister and from the provincial assembly.