High profile security surrounds Justin Trudeau as he arrives at a rally in Mississauga, Ontario. AP

Canadian Prime Minister Justin Trudeau donned an armored vest and appeared with a heavy security detail at a major election rally on Saturday.

Officials would not reveal the nature of the threat. It resulted in a 90-minute delay before Trudeau appeared before about 2,000 supporters who had turned out as the election campaign ahead of the Oct. 21 vote.

Trudeau wore a suit jacket rather than his usual rolled-up sleeves and loosened tie, and was wearing a vest, which was noticeable in photos taken at the event.

Trudeau was escorted through crowd by a large number of plainclothes Royal Canadian Mounted Police officers as well as Mounties dressed in green tactical gear.

Canadian Prime Minister Justin Trudeau and his wife Sophie walk arrive at Pearson airport in Toronto on Saturday. AP

RCMP spokeswoman Stephanie Dumoulin said for security reasons they do not comment on security measures given to the prime minister. A spokeswoman Trudeau also declined comment.

Prepared remarks had indicated that Trudeau's wife, Sophie Gregoire Trudeau, was to introduce the Liberal leader. She did not appear or take the stage during the rally.

"Very upsetting to hear that Justin Trudeau had to wear a bulletproof vest tonight at a campaign event," opposition Conservative leader Andrew Scheer tweeted. "Threats of violence against pollical leaders have absolutely no place in our democracy."

Opposition NDP Leader Jagmeet Singh was the first to tweet his concern.

"Any threat made against @JustinTrudeau, or any leader, is troubling to all of us," he wrote. "No matter how you vote or believe, no one should face threats of violence. To the officers who protect all of us - thank you."

Associated Press