Nick Kyrgios has been fined by the Association of Tennis Professionals for unsportsmanlike conduct after walking out of his first-round match at the Shanghai Masters.

The controversial Australian stormed off the court to boos from the crowd after losing the first-set tie-break 7-5 to American opponent Steve Johnson.

Shortly after receiving a warning for whacking two balls out of the court in frustration, the 22-year-old threatened to walk away midway through the match if he lost the breaker.

Kyrgios later took to Twitter to apologise to the fans, blaming his walkout on a stomach bug.

As a result of his actions, the tennis star has been fined £7,500 and also lost £16,000 in prize money due to his failure to get signed off for a medical despite complaining of feeling poorly.

Last season at the tournament, the Australian served an ATP Tour ban for a lack of effort in a second-round match against Mischa Zverev.