The Royal Canadian Mounted Police is scheduled to hold a press conference at the Toronto international airport at 3:30 pm (1930 GMT) to provide details.
Canada's public broadcaster meanwhile said federal police and intelligence agents, as well as their US counterparts, were involved in the year-long investigation that led to arrests in Toronto and Montreal.
"I cannot confirm any details. These will be provided at the press conference," RMCP spokesperson David Fallf told AFP.
The news comes one week after the twin bombings at the Boston Marathon killed three people and wounded 180, and as Canada's parliament debates a proposal to beef up anti-terror measures.
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