Canada says 80 citizens and immigrants who recently returned from war zones including Iraq and Syria are suspected of having links to "terrorism" groups.
The suspects were planning "terrorist activity" on Canadian soil and are accused of working with the Islamic State organisation in Iraq and Syria, where a US-led coalition is launching air strikes against the jihadists.
"These dangerous individuals have a desire to commit terrorist activity and pose serious threat to law-abiding Canadians," Public Safety Minister Steven Blaney said.
The comments come a day after Canadian lawmakers voted to join the air campaign against Islamic State militants in Iraq.
The 80 suspects are accused of violating Canadian law, which criminalises participation in "terrorist" activities abroad.
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They are now under investigation by the Royal Mounted Canadian Police, "which will seek to put them behind bars where they belong", Blaney said.
"Those who associate with this barbaric group should face the full extent of Canadian law," he added, referring to Islamic State militants.
An additional 50 people with links to Canada are suspected of being involved in "terrorist activities" and remain abroad, he said.
Not all the suspects are returning from Iraq and Syria, and they are accused of belonging to several groups in addition to IS, said Canadian Security Intelligence Service director Michel Coulomb.
"We have Canadians in Pakistan, Afghanistan, Yemen, Lebanon, in the Sahel, in the Maghreb, that are involved in terrorist-related activities," Coulomb said.
The activities could include fundraising or propaganda, he added.
Canada says it plans to send 600 air crew and other personnel to Iraq, along with six fighter jets and several other military aircraft.
According to US intelligence estimates, 15,000 foreign fighters from 80 nations have joined the ranks of jihadists in Syria.
