Usain Bolt has admitted that he was "sluggish" out of the blocks on Saturday as he made his Rio Olympics debut during qualifying for the men's 100m.

The Jamaican comfortably qualified for the semi-finals of the event, winning his heat with a time of 10.07s, but ranked as the fourth-fastest athlete overall during the qualifiers and was sixth-hundredths of a second slower than the USA's Justin Gatlin.

"I'm happy to get the first one out, it felt okay. It wasn't the best start. I feel kind of sluggish. I think it's the fact that it's the morning. I'm not usually running this early in the morning," said Bolt, whose heat got underway at 12.42pm local time.

"Hopefully tomorrow I can go much smoother. I'm feeling good, I'm happy. Now it's all about execution and getting it right when it comes to the final."

Bolt is in Brazil hoping to complete an unprecedented 'triple-triple' by winning golds in the 100m, 200m and 4x100m for the third time.