The Games, due to run until September 30, are expected to feature 550 athletes from 17 countries participating in 12 sports.

Prince Harry, who founded the Invictus Games in 2014 for wounded or traumatised war veterans, described all those competing as being winners.

He said "the direction of [his] life changed forever" after serving in the military, between 2005 and 2015, and he knew he had to use his "great platform to advocate for service people".

"Some of you have cheated death, and come back even stronger than before," Prince Harry was reported as saying by the Toronto Star.

"You are all winners.

"You are Invictus, let’s get started."

Led by flagbearer Phil Badanai, hosts Canada’s team of 90 athletes rounded out the traditional Parade of Nations at Toronto’s Air Canada Centre.

Prince Harry sat next to United States First Lady Melania Trump during the Opening Ceremony.

He was a row above Canadian Prime Minister Justin Trudeau, who also delivered a speech.

"You’re not just here to inspire, you’re here to win," Trudeau said in addressing the athletes.

"You will show the world that illness and injury can actually be a source of tremendous strength.

"We know that no one leaves a battlefield unchanged, and that not all scars can be seen.

"Asking for help when you have physical and mental injuries, that’s hard for everyone.

"But it’s especially tough for people like you who have dedicated your lives to helping others."

Earlier in the day, Invictus Games competitors from The Netherlands and Great Britain were greeted by Prince Harry as they competed for the first gold medal of the Games in the Jaguar Land Rover Driving Challenge.

Prince Harry awarded medals to the top finishers with the team from The Netherlands taking top honours, Britain finishing second, and Denmark coming third.

The inaugural Invictus Games were held in London in 2014.