Norway's Jakob Ingebrigtsen broke his own European 1500 metres record at Sunday's Diamond League meeting in Silesia, clocking 3:27.14.
The 22-year-old followed the field until the final lap, when he sprinted clear, beating the previous record by 0.81 seconds set in Oslo last month, sending a warning shot to rivals ahead of the upcoming World Athletics Championships in Budapest next month.
"I am always focusing on myself in races. Today I wanted a fast race and I wanted to run another sub-3:28," Ingebrigtsen said.
"This result was the best I could hope for today."
He fell short of the world record of 3:26:00, set by Morocco's Hicham El Guerrouj 25 years ago in Rome, by over a second.
"You cannot always think about records. Today I wanted one, but I will now be focusing completely on getting ready for the World Championships," he said.
Kenya's Abel Kipsang finished second, crossing the line almost two seconds after Ingebrigtsen in 3:29.11.
Akani Simbine of South Africa grabbed his second Diamond League 100m win in a row, clocking 9.97 seconds, with the first four separated by just 0.02 seconds. American Fred Kerley took second place, experiencing his first defeat of the season.
"I know I am the first to beat Fred this year, we have a good friendship, a good rivalry. I am very satisfied with my performance and hope to continue my good form," Simbine said.
Kerley appeared unaffected by the loss.
"I feel good about today's race. Nothing was missing. I got my job done."
American Sha'Carri Richardson won the women's 100m, with a time of 10.76 seconds. She edged out Jamaica's Shericka Jackson by 0.02 seconds, securing her second 100m Diamond League win of the year.
"I love the time. I put a great race together. This was a great competition, it was amazing. I executed correctly," Richardson said.
Yulimar Rojas from Venezuela set a new world lead of 15.18m to win the women's triple jump.
Poland's Natalia Kaczmarek gave the home crowd something to cheer when she comfortably won the women's 400m with a personal best time of 49.48.
"Things looked good in training, but I was not quite able to translate it into competition. Now things finally worked out," Kaczmarek said.
Favourite and world record-holder Armand Duplantis cleared 6.01m to win the men's pole vault ahead of American Sam Kendricks.