Approximately 1,500 people converged on Toronto's Nathan Phillips Square on Saturday to protest the federal government's proposed anti-terror bill, one of 55 rallies planned across the nation on what is being called a "national day of action" against Bill C-51.

Signs reading "Bill C-51 is un-Canadian" and "freedom not feardom," among others, poked through the sea of cheering, nodding and chanting heads, the sound of drumming pulsing behind them.

The wide-ranging bill would give police much broader powers and allow them to detain terror suspects and give new powers to Canada's spy agency.

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Protesters expressed concerns that the bill would infringe on the civil rights and freedoms of Canadians.

"It creates an environment where you're guilty until proven innocent and that's not who we are in Canada. We have stronger values than that," said protester Ayesha Khan.

"Yes, [terrorists] need to be stopped but not this way," she said.

Other major cities holding protests included Vancouver, Montreal and Ottawa, where hundreds of chanting protesters clogged the street outside Prime Minister Stephen Harper's office before marching onto the grounds of Parliament Hill.

Critics say the bill, if enacted as law, will infringe upon Canadians' civil liberties and right to privacy, especially online.

"I'm connected on Facebook, Instagram, various social media platforms," said Toronto protestor Jared Goldman. "Even though I don't do anything illegal, my information could be used to target me a as terrorist."

Many prominent figures took to the stage at Nathan Phillips Square to vocalize their opposition of the bill.

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Toronto-based human rights lawyer Paul Copeland called C-51 the "most dangerous act" since the War Measures Act of 1970. That statute provided police services with the power to search and arrest Canadian citizens without warrant.

NDP MPs Peggy Nash and Andrew Cash also spoke at the rally, fiercely supporting those who oppose the bill.

"For centuries, generations before us fought for the liberties that make us who we are today…Our citizens have the right to speak up," Mr. Cash said.

NDP Leader Thomas Mulcair spoke at the rally held in Montreal. "C-51 is a bill that could seriously endanger our right to protest peacefully, to stand up against a government or an infrastructure or an economic policy," he said. "Mr Harper has never been able to give a single example of why this bill is necessary."

In Toronto, Green Party Leader Elizabeth May spoke, using the opportunity to bash both the bill, and the prime minister.

"[Mr. Harper] wants Canadians to be scared out of their wits. He wants us to be scared of everyone; different cultures, different religions. He wants us to be divided and fearful…. Canadians will not be scared out of their rights," she said.

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Ms. May also urged for Liberal leader Justin Trudeau to oppose the bill.

Meanwhile, the Conservatives continued to emphasize their commitment to C-51.

"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," a spokesperson for Mr. Blaney told The Globe in an email statement.

Core organizers of the "national day of action" event include BC Government and Service Employees' Union (BCGEU), the advocacy group Leadnow, and Open Media, an organization dedicated to online rights.

The event also gained social traction, with the hashtag #StopC51 trending in Canada.

"We really want to make the largest call possible across the country to show how opposed Canadians are to what's in this bill," said Open Media's communications manager David Christopher.

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"Getting thousands of Canadians on the streets will send Stephen Harper a message he won't be able to ignore."

With a report from The Canadian Press