The lawyer for twin brothers charged with terrorism-related offences says his clients intend to "vigorously defend" themselves against the allegations.

Carlos Larmond, 24, and Ashton Carleton Larmond, also 24, were arrested Friday following what the RCMP called a "national security criminal investigation."

Carlos Larmond, who was arrested in Montreal at the Pierre Elliot Trudeau Airport, has been charged with attempting to leave Canada to participate in terrorist activity abroad, and participating in the activity of a terrorist group.

Ashton Carleton Larmond was arrested in Ottawa, and charged with facilitating terrorist activity, participation in the activity of a terrorist group and instructing to carry out activity for a terrorist group.

The brothers were raised in Canada and graduated from an Ottawa high school in 2008.

Lawyer Joseph Addelman, who is currently representing both brothers, described the charges as "serious."

"They carry possibility of life in prison," he told reporters in Ottawa on Saturday. "Obviously they’re very serious allegations that the public is going to be concerned about, the justice system is going to be concerned about."

However, Addelman described the case as a matter of religious freedom. He said both his clients are Muslim.

"All Canadians have the right to express their religious beliefs and to participate in free assembly without that being a criminal offense," he told reporters.

On Saturday, the brothers appeared separately in court via video link.

Dressed in a hoodie and wearing his beard shortly trimmed, Carlos Larmond looked straight at the camera for the majority of his fifteen-minute appearance. The only words he spoke were "yes ma'am," to acknowledge Judge Louisette Girault’s instructions that he not contact his brother.

Ashton Carleton Larmond, appeared shortly after at 11 a.m. for his five-minute hearing, wearing a black sweater with long hair and a long beard. He also stared at the camera and only spoke the words "yes ma'am," when told not to contact his twin.

Crown Prosecutor Rod Sonley said the brothers have been adjourned until Feb. 12. By that date, Addelman said the two will have separate counsel.

Speaking from Paris, where he is visiting the sites of recent terror attacks in the city, Public Safety Minister Steven Blaney said the Larmond arrests were part of an ongoing investigation and that Canada is committed to fighting terrorism.

Blaney added that the brothers' arrests are not directly linked to the Paris attacks.

"They are not linked in itself by exact link but they are part of this extremist ideology and in that way they are related but not necessarily in the same cell or groups," Blaney said.

The pair remain in police custody and are expected to be back in court in February.