Monaco, Principality of Monaco: Qatar's Abderrahman Samba, returning from an injury, hit his stride straight away to finish second in 400m at the Diamond League meet in Monaco on Friday.
Gardiner Steven of Bahamas clocked 44.51 to win the event, while Samba was equally impressive with his time of 45.00.
"I'm so happy with my time," said Samba. "I'm just back from injury - I missed a few weeks but it's all good now. I felt like I got my rhythm back."
Nathan Strother of the US came third in 45.54.
Meanwhile in the other headline acts, controversial American Justin Gatlin outsprinted up-and-coming compatriot Noah Lyles in the 100 metres while Sifan Hassan set a new world best in the women's mile.
In balmy conditions at a packed Stade Louis II, the 37-year-old Gatlin kept both his nerve and form after an average start to streak through the finish line in 9.91 seconds, just one-hundredth of a second ahead of much-vaunted Lyles, 21.
"It was a technical race tonight," said Gatlin, the 2004 Olympic gold medallist and current world champion who served a doping ban between 2006-10.
"I just kept focused as I knew Noah would be coming after me like a bat out of hell!" Gatlin told AFP.
There was an outstanding performance in the women's mile, which is not an Olympic or world distance, as Ethiopian-born Dutch runner Hassan came home in 4min 12.33sec, smashing by 23 seconds the previous best set in 1996 by Russian Svetlana Masterkova.
Hassan, twice European champion over 1500m and once 5000m gold medallist, cracked the field with two laps to go and streaked through the line with teeth gritted, collapsing as the timer flashed up her feat.
"The first 800m was a bit slow so I wasn't thinking it would be a world record," said Hassan. "When I crossed the line I was so surprised."
"After you run the last 400m like that and set a world record it gives you so much confidence over 5000m," said Hassan, who will aim for a 1500-5000m double in the September 28-October 6 world championships in Doha.
Another experienced campaigner, Botswana's Olympic silver medallist Nijel Amos, produced a stunning meet record in winning the men's 800m in 1:41.89 ahead of Kenya's Ferguson Rotich, France's world champion Pierre-Ambroise Bosse only managing ninth in a high-quality race.
Only four runners have gone faster than Amos' time, which was the 15th fastest ever run over the distance.
"Everything has been good in the last few weeks and I knew I could run 1:41 today," said Amos.
"The world record is not on my mind but if I'm patient, it will come."
McLaughlin dominates hurdles
Kenyan Timothy Cheruiyot cruised to victory in the men's 1500m in 3:29.97, European 1500 and 5000m champion Jakob Ingebrigtsen -- still just 18 -- coming in second.
American teenager Sydney McLaughlin kicked off the evening in impressive style, setting a world-leading 53.32sec in the 400m hurdles.
The 19-year-old led from the first hurdle and scorched around the track in muggy conditions, with temperatures of 28 degrees Celsius (82F) and high humidity.
There was further US success as world indoor champion Kendra Harrison streaked to a 100m hurdles win in a season's best 12.43sec.
There was no Caster Semenya in the women's 800m won by American Ajee Wilson.
The South African double Olympic is not appearing in the Principality despite having been cleared to run during her appeal at attempts by the Monaco-based world governing body for athletics, the IAAF, to introduce rules requiring female athletes in events between 400 and the mile to take medication to reduce high testosterone levels.
In her absence, Wilson won easily in 1:57.73, almost three seconds off Semenya's best for the season.
A loaded field in the women's 200m saw Shaunae Miller-Uibo of the Bahamas, the reigning Olympic 400m champion, win in 22.09sec ahead of Jamaica's Elaine Thompson, who won the sprint double in Rio, and two-time defending world 200m champ Dafne Schippers of the Netherlands.