Olympic champion Usain Bolt's rare defeat in the 100m in Rome on Thursday was not down to a flare-up of the hamstring injury, which has hampered his start to the season.

Bolt was beaten into second place at the Diamond League meeting, 0.01 seconds behind London Games bronze medalist Justin Gatlin, who won in 9.94.

Despite a good start, world record holder Bolt looked labored and was unable to pull away from the field, giving Gatlin the chance to edge a thrilling race.