Justin Gatlin confirmed his credentials as firm favourite for a world sprint title with another convincing victory at the Diamond League on Friday, while Genezebe Dibaba raced to an incredible world record.

Gatlin, who has served two doping bans, scorched through the 100m line in 9.78 seconds ahead of teammate Tyson Gay (9.97) for his 27th successive sprint victory.

"I rate this race as good as the other ones this year," said Gatlin, unbeaten since August 2013 and who will now return to train at his Florida base of Orlando ahead of the August 22-30 world championships in Beijing.

"It was the first one this season run after a relay so I think without that I could have been faster," he said in reference to a rare earlier outing for the US relay team also comprising Gay, Trayvon Bromell and Michael Rodgers, who won in a fast 37.87sec.

In a thrilling night of track and field at the Stade Louis II, with personal bests abound and six world-leading performances, Dibaba took the crown with an astonishing world record in the women's 1500m.

The previous best of 3:50.46 had been set by China's Qu Yunxia in Beijing in 1993. That and other quick times in the discipline were mainly run by Chinese athletes in the 1990s under the guidance of controversial coach Ma Junren.

Six of Junren's athletes were dropped from China's team for failing dope tests ahead of the Sydney Olympics in 2000.

Victory for Dibaba, the two-time world indoor champion, never looked in doubt, and aided by two pace-setters in perfect running conditions, the 24-year-old Ethiopian came home in 3:50.07 to shatter the old record.

"The pacemakers finally did a good job," said Dibaba, who also holds the world indoor records over 1500, 3000 and 5000m.

"I'm the first from Ethiopia to get a 1500m world record and that is amazing. I think Tirunesh will be happy," she said in reference to her multi-medal winning elder sister who holds the outdoor 5000m world record.

"One thing is clear: I will double at the world championships and let's try for the 5000m world record in Beijing."

There was another remarkable performance in the men's 1500m by two-time defending world champion Asbel Kiprop.

The tall, lean Kenyan, also the 2008 Olympic gold medallist, clocked 3min 26.69sec -- the fifth fastest 1500m ever run and also the fastest run in 14 seasons which leaves him the third fastest performer of all time.

His blistering pace was too much for Briton Mo Farah, racing his second event since allegations his coach Alberto Salazar violated anti-doping rules.

"At the bell I knew it could be a very fast time," said Kiprop. "I wanted a bit of a faster time. But all things considered, it's great and confirms my form before Beijing."

World and Olympic 5000-10,000m champion Farah came in fourth in 3:28.93, missing out on his own European record by just 0.12sec.

"It was good to be in that company," acknowledged Farah. "I wanted to run hard, not just a race and it worked.

"As for the double in Beijing, I will do the 10,000m for sure and then we will see about the 5000m."

Algeria's Olympic champion Taoufik Makhloufi claimed second ahead of Morocco's Abdelaati Iguider, world indoor champion and bronze medallist at the London Games, both athletes finishing in personal bests, as did seven others in the field.

There was an impressive victory in the men's 800m for unheralded Bosnian Amel Tuka, who won in a world leading time of 1:42.51 ahead of Botswana's Nijel Amos. He also became the fourth fastest European over the two-lap race.

"I don't know what happened," said the Verona-based Tuka. "You need to ask my coach as to why there's such a big improvement. My goal for this season was 1:45!"

American Joe Kovacs managed a best of 22.56m in the shot put, the 13th farthest in history and the best since 2003, with compatriots Christian Cantwell and Rees Hoffa completing the all-US podium.

Frenchman Renaud Lavillenie, the world record holder, rediscovered his pole vaulting mojo for Beijing after stuttering through the last couple of events. 

He managed a best of 5.92m for victory, going close three times at 6.02.