TORONTO  The charges are sweeping. The Royal Canadian Mounted Police say that three Canadians, among them a physician, were plotting to blow up targets in Canada and funnel funds to Afghanistan to insurgents fighting against Canadian soldiers.

But even as the police arrested a fourth man on Friday in what they call Project Samosa, they resisted making public many details of what the men were accused of planning or doing. Canadian officials, including Prime Minister Stephen Harper, talked ominously, however, about the threats of terrorism the case represented.

After Khurram Syed Sher, a pathologist from London, Ontario, appeared to be formally charged in an Ottawa court, even his lawyer, Anser Farooq, said that he knew almost nothing about the specifics of the case.

Dr. Sher, whose remarkably unsuccessful tryout for “Canadian Idol” developed a following on YouTube after he was arrested Thursday, was charged with conspiracy to facilitate a terrorist offense. Misahuddin Ahmed, a 26-year-old X-ray technician, faces the same charge. In addition to the conspiracy charge, Hiva Alizadeh, 30, of Ottawa, was also charged with financing a terrorist plot and possessing explosives with intent to kill and injure. The Royal Canadian Mounted Police offered no information about the fourth person who was arrested. He was released later on Friday, the Canadian Broadcasting Corporation reported.