World and Olympic champion David Rudisha cruised to victory in the 800 metres at the season-opening Diamond League meet in Doha on Friday, and Justin Gatlin clocked the second fastest time of the year to win the 100 on a strong night for the Americans.

Rudisha's time of 1 minute, 43.87 seconds was significantly slower than the 1:40.91 he ran to break the world record at the 2012 London Olympics.

After the pacemaker retired midway through the race, Rudisha surged to the front and was never threatened. He beat Mohammed Aman by more than a half second, avenging a loss to the Ethiopian at a Diamond League event in Zurich last year.

"I feel good. I was relaxing today," Rudisha said. "It was the beginning of the season and it was first race, so there was no pressure. [Aman] defeated me in the last race of the season, and it was good to do something at least in the beginning of the season to give me more confidence."

Gatlin started slowly out of the blocks but came home in the final 20 metres to edge out compatriot Mike Rodgers at the line with a time of 9.97. The lineup was weaker than in previous years, with Yohan Blake pulling out injured and Usain Bolt not scheduled to compete.

"It was good. Mike has been running a really good season, so I knew he would be really good competition coming into Doha," said Gatlin, the 2004 Olympic champion who returned from a four-year doping ban in 2012. "I was feeling under the weather coming into the competition. I had a fever, found out I had a sinus infection. I still wanted to come here and thought I would be ready. I was ready at the last second."

Countryman Tyson Gay holds the year-leading time of 9.86, while Bolt opened his season by running 10.09 in the Cayman Islands earlier this week after recovering from a minor hamstring strain.

"Being a seasoned vet in the sport, I know not to get really flustered with fast times for the beginning of the season," Gatlin said. "It is going to be a long season. It is about the person who can pace themselves who can have those fast times crossing the finish line at the finals."

American athletes won six of the 16 events and there were meet records for Olympic women's long jump champion Britney Reese and Ryan Whiting in the men's shot put. Reese leapt 7.25 metres, and Whiting threw 22.28 metres in an event in which Olympic gold medallist Tomasz Majewski finished sixth.

The only setback was Allyson Felix, whose 10-race winning streak in Doha came to an end when she came second in the 400 behind Amantle Montsho of Botswana. Felix hadn't run the 400 since the 2011 world championships, a race she also lost to Montsho.

Two-time Olympic 100 champion Shelly-Ann Fraser-Pryce led Sherone Simpson in a 1-2 Jamaican finish in the 200, a race she is expected to compete in at the world championships in Moscow. Fraser-Pryce was runner-up over the distance in London.

"Overall, I'm just happy to come away with a win," Fraser-Pryce said. "Today I didn't run according to how I wanted but still came out with a victory. That made me happy. There is a lot more room for improvement in the 200, and I'm looking forward to more races to see how best I can put a complete race together."

Canadians Kimberly Hyacinthe and Crystal Emmanuel were fifth and eighth in the race, respectively.

Montreal's Hyacinthe crossed in 23.07, with Emmanuel clocking 23.40.