An Israeli soldier died of heat stroke while running the Tel Aviv marathon on Friday while four were hospitalized in critical condition.
More than 30,000 runners reportedly ignored Health Ministry warnings to take part in the event, run in 90-degree heat.
Shalom Life named the soldier as Michael Michaelovitch, 29, an IDF sergeant from Tene, south of Hebron.
The website said Michaelovitch had competed in such events before and "trained well" for this one.
He was rushed to Tel Aviv’s Sourasky Medical Center but could not be revived.
Haaretz quoted runner Vered Yeshula of Ramat Gan, participating in the half-marathon, as saying:
"The heat was so intense that many runners switched to a walking pace. At the [12-mile] mark, I saw a man stretched out on the ground with paramedics attending to him."
Fifty runners were treated in a tent set up on the course, Haaretz wrote, mostly for heatstroke and dehydration, and of the 32 taken to the hospital some were unconscious and on respirators.
The Associated Press cited Israel's public security minister, Yitzhak Aharonovich, as saying on Israel Radio that the incident was "very serious" and suggesting that race organizers could be held responsible for not cancelling the race after heat was predicted.
The Tel Aviv municipality defended its actions, saying it had followed the instructions of health officials.
The full marathon of 26.2 miles was postponed in anticipation of the heat wave, while the half-marathon of 13.1 miles was started earlier in the morning to avoid the peak of the heat wave.