Organisers of an annual horse festival in Japan where riders dressed as samurai re-enact battles said Tuesday they were considering changing dates for the gathering next year, after sunstroke affected 111 animals, killing two of them.

Japan has recorded its hottest average July temperatures in over 100 years, and on Tuesday heatstroke alerts were in place in 26 out of 47 prefectures, with the mercury forecast to hit 38 Celsius (100 Fahrenheit) in places.

At least 111 horses -- and dozens of people -- needed treatment for sunstroke at the Soma Nomaoi festival in Fukushima prefecture from July 29 to 31, after temperatures touched 35 degrees, the hottest in five years, organisers said.

Two of the animals died, they said.

The annual three-day event, which features more than 400 participants dressed as medieval samurai warriors fighting on horseback over flags that are shot overhead by fireworks, attracted more than 120,000 people, reports said.

Yoshichika Hirata, a member of the festival's executive committee, told AFP that changing the date of next year's event to a cooler period would be discussed at a meeting on Thursday.

"We sprinkled water on the track for the first time, as extreme heat was expected. We used three water-sprinkler cars, but water dried up quickly," Hirata said.

One horse died during last year's festival, after which a majority of riders supported a plan to change the date, according to a survey done in December.