In the first major meet of a season all but wrecked by the COVID-19 pandemic, Cheptegei raced clear on a balmy night at Stade Louis II to clock 12 minutes 35.36 seconds.

Cheptegei, the 2019 world champion over 10,000m, took 22 seconds off his lifetime best at 5,000m.

"Monaco is a special place and it's one of these places where I could break the world record," said Cheptegei, who has trained in Uganda instead of Europe this year.

"It took a lot of mind setting to keep being motivated this year because so many people are staying at home but you have to stay motivated."

Australian Matthew Ramsden was among the pacemakers who helped to set up the race for Cheptegei.

Kenya's Nicholas Kimeli, who was just approaching the final straight as Cheptegei crossed the line, finished a distant second in a lifetime best of 12:51.78.

American world champ Noah Lyles won the men's 200m in 19.76.

"I've got high expectations for myself so I'd say the race got the Noah stamp of approval but I wouldn't say it got the Noah satisfaction stamp," said Lyles, whose brother, Josephus, was runner-up in 20.30.

Norwegian teenager Jakob Ingebrigtsen set a European record in the 1500m with 3:28.68 - 0.13 faster than Britain's Mo Farah at Monaco in 2013.

It still left Ingebrigtsen runner-up in a standout race won by Kenyan world champion Timothy Cheriuyot in 3:28.45.

In the women's 5000m, world champion Hellen Obiri from Kenya broke clear in the last 200 meters to win in a world-leading 14:22.12.

Jessica Hull broke the 18-year-old Australian record by finishing fourth in 14:43.80.

Five thousand socially-distanced fans were allowed into the 16,000-capacity stadium.

The next meet of the cut-down Diamond League circuit is on August 23 in Stockholm.

Australian Associated Press