EUGENE (Reuters) - Former Olympic champion Justin Gatlin won the men's 100m at Saturday's Prefontaine Classic, the fourth leg of the Diamond League athletics' series.

The 31-year-old American, who won gold at Athens in 2004, then bronze in London last year after serving a doping ban, won the blue-riband sprint in a wind-assisted time of 9.88 seconds.

It was his second Diamond League win this season after he also won in Doha last month.

With the World Championships looming in Moscow in August, most of track and field's biggest names have been slowly getting back to action in the Diamond League series, although Jamaican sprinter Usain Bolt has been a notable absentee because of a hamstring injury.

Bolt's countrywoman, two-time Olympic champion Shelly-Ann Fraser-Pryce, won the women's 100m dash at Eugene, Oregon on Saturday while America's LaShawn Merritt won the 400m.

Britain's double Olympic champion Mo Farah was beaten in his first Diamond League race of the season. The 30-year-old finished second in the 5,000m behind Kenyan Edwin Soi After pulling out of the 10,000m because of a stomach virus.