Uchimura, the double Olympic all-around gold medallist, suffered an ankle injury after landing his vault awkwardly at the Montreal Olympic Stadium.

After an excellent jump, the Japanese star was visibly hurt and was clutching his left ankle as he limped away from the podium.

The 28-year-old, who has 19 World Championship medals to his name, then put on a brave face in his subsequent parallel bars routine but again stumbled on the landing.

As a result of the injury, Uchimura pulled out of the horizontal bar rotation, which brought the reign of "King Kōhei" to an unfortunate end.

"I feel very sorry for the people who came to support me," Uchimura told NBC Sports.

"I apologise to my team-mates.

"After the vault, I couldn't even walk.

"I just wanted to keep trying to finish the competition."

Uchimura's withdrawal means that a new all-around world champion will be crowned for the first time since 2009 during the final on Thursday (October 5).

Cuba's Manrique Larduet, all-around silver medallist behind the Japanese at the 2015 World Championships in Glasgow, finished the opening day at the summit of the leaderboard with a score of 86.699.

Oleg Verniaiev of Ukraine, who was expected to be the main challenger to Uchimura and came close to beating the Japanese at Rio 2016, was second on 85.431 points, with Yul Moldauer of the United States third on 84.331.

Men's qualification continues tomorrow, while the first two women's qualifications subdivisions are also due to take place.