American Christian Coleman signalled a return to form and fitness by edging out compatriots Ronnie Baker and Noah Lyles to win a thrilling Diamond League 100-metre race in Rabat, while Hellen Obiri set a new world-leading time in the women's 5,000m.
The 22-year-old set a 60m world record of 6.34sec earlier this year, but has struggled with injuries since.
"It was a perfect night for me -- good race and good time, I couldn't be happier," he said.
"I am not so surprised to win on my first race (back), even with such a great field because I was very fast in practice these last days. When I was injured, I managed to keep a good condition."
Baker and Lyles share the world-leading time of 9.88 for 2018.
The former finished in the same time as Coleman but was beaten on the dip, while Lyles was just one hundredth of a second slower.
Michael Rodgers underlined the Americans' dominance by coming fourth, as Britain's Reece Prescod was lucky to avoid disqualification for a false start and was fifth.
- Obiri shows her class -
Kenya's Obiri, the reigning world champion and 2016 Olympic silver medallist, powered clear of Sifan Hassan to win the women's 5,000m in a magnificent time of 14 minutes and 21.75 seconds.
"The race was fast and difficult, especially in the last lap," said Obiri.
Elsewhere, Russian high jumper Mariya Lasitskene saw her 45-competition unbeaten run come to an end, as she failed to clear a modest 1.94 metres.
The 25-year-old had not lost since June 2016 and has won gold medals at each of the last two world championships.
But her disappointing performance in Morocco allowed Bulgarian Mirela Demireva to snatch the win with 1.94m, although she later brought down the bar when attempting a personal best of 2.02m.
She was cleared to resume competing internationally last year as a neutral athlete.
South African middle-distance great Caster Semenya eased to victory in the rarely-run 1,000m event, posting a time of 2:31.01, before she heads to London to attempt the 800/1500m double in the World Cup.
"It was a very good race, but unfortunately it wasn't as fast as I expected," she said.
Olympic 400-metre champion Shaunae Miller-Uibo of the Bahamas ran down Britain's Dina Asher-Smith to win the 200m in 22.29sec, while Olympic gold medallist Brianna Rollins-McNeal cruised to 100m hurdles victory in 12.51sec.
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