Kyrgios, who is known for his temperament and on-court antics, was heard threatening to retire if he lost the first set tie-break at the Qizhong Forest Sports City Arena.

The 22-year-old, who had made the claim after becoming frustrated with the crowd inside the arena, subsequently quit the match after Johnson served an ace to clinch the opener 7-6.

His decision was greeted with a chorus of boos as he walked off court.

The fiery Australian, who was deducted a point during the match for an audible obscenity and was also warned for smashing two balls out of court in protest at a line call, later took to Twitter to insist a stomach bug and a shoulder problem were the reasons behind his retirement.

"Guys I want to apologise to the fans in Shanghai and those that watched around the world on TV today," Kyrgios, who lost in the China Open to Rafael Nadal before arriving in Shanghai, said.

"I've been battling a stomach bug for the last 24 hours and I tried to be ready but I was really struggling on the court today, which I think was pretty evident from the first point.

"My shoulder started to hurt in the practice today, which didn't help either, and once I lost the first set I was just not strong enough to continue because I've not eaten much for the past 24 hours.

"I'm gutted to be honest as I was keen to keep the good momentum that I built in Beijing going and finish the year strong. 

"I'll do what I can to make sure I do."

Elsewhere, Juan Martin del Potro, the 2009 US Open champion, booked his place in the last 16 with a comfortable 6-3, 6-4 win over Russian Andrey Rublev.

Croatian Marin Cilic, the fourth seed, also progressed by beating Britain's Kyle Edmund 6-3, 7-6.