Thousands of demonstrators gathered across the country on Saturday to rally against the Conservative government's proposed anti-terror legislation, which seeks to expand the powers of police and spy agencies.

The government, which introduced Bill C-51 in January, insists that it provides law-enforcement authorities with the vital tools needed to stamp out terror plots before they unfold.

But critics say the bill lacks appropriate oversight, and could compromise Canadians’ personal liberties.

Demonstrations attracted protesters to some 55 locations from coast to coast, where organizers called Saturday a "national day of action" against the anti-terror measures.

In Toronto, hundreds of people gathered at Nathan Phillips Square to voice their outrage over the legislation. Many carried signs and chanted in protest over the bill, which they say infringes upon their rights and freedoms.

"We need to be talking about how we build in some meaningful processes that keep Canadians safe, while not trampling on our rights, and that have oversight," Kim Fryer, a teacher and protest organizer, told CTV News Channel.

Blair Buchanan and his wife Lisa-May attended the event with their 8-month-old daughter and a sign that read "Defend our Freedom."

Lisa-May says that while the threat of terrorism is "real," legislation should properly consider both the importance of security, and the rights of Canadians.

"It definitely needs to be dealt with, but there are better ways to do it and it needs to be thought out more. Don’t rush this -- take your time do it properly the first time," she said.

Blair, who is part of a labour union, also expressed the concerns that the bill could potentially lead to spying on political activists and movements.

"That absolutely takes away our freedom of speech, and that's … ridiculous," he said.

Protesters at the rally marched to Canadian Security Intelligence Service office in downtown Toronto.

Conservatives maintain that the legislation is necessary to combat the increasing risk of global terrorism, and that the bill will not infringe upon Canadians' civil liberties.

Defence Minister Jason Kenney said in a statement released on Saturday saying that the "international jihadist movement has declared war” on Canada.

"Our government has put forward measures that protect Canadians against jihadi terrorists who seek to destroy the very principles that make Canada the best country in the world," Kenney said.

"Canadians understand that their freedom and security go hand in hand … (and they) expect us to protect both … there are safeguards in this legislation to do exactly that," he added.

Bill C-51 is the latest example of the Conservative government's tough-on-crime strategy. The anti-terror legislation would give CSIS the ability to actively disrupt terror plots, expand no-fly list powers and allow police to have greater control in limiting the movement of a suspect.

The bill would also allow for increased intelligence-sharing between law-enforcement authorities.

Justice Minister Peter MacKay told CTV Atlantic that protests like the ones being held across Canada Saturday will not be affected by Bill C-51.

"One of the great ironies is that criticism that has been levelled against the bill is that peaceful protest won't be tolerated, well this is an example of peaceful protest happening in Canada that will be absolutely tolerated and it is part of the democratic process," MacKay said.

The minister also said that it was necessary to modernize law-enforcement powers with "proper oversight," so authorities can "pre-emptively" deter and prevent terrorist acts.

"There are those sadly who would do us harm, and we have examples of that in our recent past," MacKay said. “And were concerned about it to such a degree that we believe that police need moderate improvements as well as our investigations that happen through CSIS.”

While the legislation will not apply to "lawful" advocacy, protest or dissent, some fear that the bill would allow authorities to crack down on activists in the name of preventing terrorism.

"As far as I understand, the language of the bill includes the power of CSIS to obtain warrants to disrupt and dismantle activities such as the demonstrations today, for example … because the definition of terrorism in the bill is so vaguely defined that they can, from what I can tell, make it up pretty much as they go long and say 'this is now a threat,'" said Krista Simon, the co-organizer of a protest held in Halifax.

Protest outside Trudeau’s office

In Montreal, hundreds of protesters marched through the streets towards the offices of Liberal Leader Justin Trudeau, who despite some reservations, has said that his party will support Bill C-51.

Among the crowd was NDP Leader Tom Mulcair, who has said previously that his party will not back the legislation

Mulcair told CTV Montreal on Saturday that the NDP will be steadfast in their opposition to the bill, which he says "compromises" the rights and freedoms of Canadians.

Mulcair said that the bill's scope is "too wide" and that existing legislation is already adequate.

"Stephen Harper is going to be going after a lot of groups that protest in a normal fashion, which has always been allowed in a free and democratic society," he said.

The bill has also received strong opposition from Canada's privacy commissioner, Daniel Therrien, who says that the bill "goes too far," and that the rights of innocent Canadians will be sacrificed in the name of intelligence gathering.

A group of four former prime ministers, including Joe Clark, Jean Chretien, John Turner and Paul Martin, have also said that the anti-terror legislation lacks "robust" accountability.

Bill C-51 is currently being reviewed by a committee in the House of Commons.

Read the full statement from the office of Public Safety Minister Steven Blaney about the C-51 protests:

"The international jihadist movement has declared war on Canada. Canadians are being targeted by jihadi terrorists simply because they hate our society and the values it represents.

That is why our government has put forward measures that protect Canadians against jihadi terrorists who seek to destroy the very principles that make Canada the best country in the world.

We reject the argument that every time we talk about security, our freedoms are threatened. Canadians understand that their freedom and security go hand in hand. Canadians expect us to protect both, and there are safeguards in this legislation to do exactly that."