Student protesters in Quebec have panned a set of laws designed to end three months of demonstrations, predicting that the newly installed legislation is likely to fuel unrest rather than quell it.

Hours after Bill 78 passed on Friday, demonstrators fanned into Montreal's downtown core to protest the controversial legislation, which they say is an affront to their civil liberties.

The protests began peacefully but took a violent turn when some demonstrators tossed Molotov cocktails into the streets. At least four people were arrested by the end of the night, according to police.

On Saturday, a march began around 8:30 p.m. local time under the watchful eye of police.

Gabriel Nadeau-Dubois, spokesperson for student group CLASSE, said at a press conference Friday that students will considering breaking the new laws if the need arises.

"By this law, the government is consciously breaking and destroying this fundamental right," he said. "It's unacceptable and if we need to break this law we will seriously consider it."

The law ends the current academic year at schools affected by the strikes, imposes fines for anyone who blocks access to university campuses and restricts the size and length of protests.

Under the new bill, anyone blocking an individual from entering a school could be fined between up to $5,000. The penalties climb up to $35,000 for student leaders and up to $125,000 for unions or student federations.

As well, student groups will have to give eight hours' notice before launching a protest and are required to provide their full itinerary. Individuals can also be punished for encouraging a protest at an institution.

Designed to bring calm to the city's streets, students say the law will instead incite more protests.

"I really think it's going to make the conflict quite worse," student Josh White Crummey told CTV Montreal. "People that were moderate are going to become radicalized. I really think it's a lapse of judgment on their part."

Student groups are not alone in their condemnation over the law. Union leaders and members of the opposition also expressed outrage over the bill Friday

Michel Arsenault, FTQ spokesperson, criticized the bill and called it "a law written by people who are very angry, people who are in a bad mood and people who are taking revenge, but also a government who lost control."

Parti Quebecois leader Pauline Marois went one step further, calling on Premier Jean Charest to meet with students and find an honourable way out of the crisis, she said.

Marois promised to scrap the law should she become premier in elections expected within the year.

However, the government maintains that the law doesn't trample on people's rights, instead it protects them.

Finance minister Raymond Bachand said the law protects students' rights to attend classes without fear.

"Nobody in Quebec anymore will be able to stop by intimidation and violence people from studying," he said. "It's a fundamental right."

The law also has the support of some business associations and institutions.

Michel Leblanc, president and chief executive of the Board of Trade of Metropolitan Montreal, said, "The objective was to pause the troubles. It was important to find a way to calm the city."