Olympic 100m champion Marcell Jacobs on Saturday withdrew from the Kip Keino Classic that got underway at the Moi International Sports Centre.
The Italian sprinter pulled out at the last minute from his long-awaited return to the track in Nairobi because of intestinal problems.
"The Olympic champion made the decision this morning with his staff, due to intestinal problems which occurred yesterday (Friday) in Kenya," wrote the Italian federation on its website.
"Marcell will not report to the starting-blocks today because he remains under observation in the emergency room of Uhai Neema Hospital, under the control of the Italian NGO World Friends," said his coach Paolo Camossi, quoted by the federation.
Jacobs was a surprise winner at the Tokyo Olympics last year. He was due to renew his rivalry with silver medalist Fred Kerley for the first time since Tokyo, Japan meet and also a duel with Kenyan sensation Ferdinand Omanyala.
Six weeks ago, Jacobs stormed to victory to take the world indoor 60m gold in Belgrade, chasing down the American world 100m champion Christian Coleman in the final. Jacobs is scheduled to compete in a 200m at the meeting in Savona, Italy, on May 18.