Italian orienteering athlete Mattia Debertolis died on Tuesday at the World Games in Chengdu, China after collapsing during competition, organisers said.

Debertolis, 29, was found unconscious during an orienteering event on August 8 and died four days later, said a joint statement from World Games organisers and the International Orienteering Federation (IOF).

The World Games is a multisport event held every four years for disciplines not included in the Olympics.

"Despite receiving immediate expert medical care at one of China's leading medical institutions, he passed away," the statement said.

It did not provide details on the cause of death.

Orienteering sees athletes navigate an unmarked course with a map and compass, punching in at designated spots along the route in the quickest time.

The event, held about 50 kilometres (30 miles) outside of central Chengdu, took place in intense heat and humidity, with temperatures above 30°C.

Debertolis, from Primiero in eastern Italy, was taking part in the final of the men's middle-distance event when he collapsed.

The six-kilometre course featured 180 metres of ascent and 20 control points that athletes must visit.

Footage from the World Games' social media accounts showed athletes running through crop fields and villages on a largely rural course.

The winner, Switzerland's Riccardo Rancan, completed the course in 45 minutes and 22 seconds.

"I needed to acclimatise quickly with hot and humid conditions. I think I managed quite well," Chinese state media quoted Rancan as saying.

Debertolis was listed as "Did Not Finish" in official results, along with 11 other athletes.

He was ranked 137th in the men's Orienteering World Rankings and had been competing since 2014, according to the IOF website.

He participated in several World Championships and World Cups as part of the Italian team.

Alongside his training, Debertolis was studying for a PhD at the KTH Royal Institute of Technology in Stockholm, where he lived.

This is the 12th edition of the World Games and it runs until August 17, with approximately 4,000 athletes competing in 253 events.

The men's middle-distance orienteering was the first medal event of the Chengdu Games.

World Games organisers and the IOF were "struck by this tragedy and extend their heartfelt condolences to the family and friends of the athlete and the whole orienteering community", the joint statement read.

"Our thoughts are with those touched by this event."

Organisers will "continue to support the family of Mattia Debertolis and the orienteering community in every possible way", it added.