Organisers of a 2021 ultramarathon in northwest China during which 21 runners died in extreme weather conditions have been sentenced to years in prison for their roles, state media reported.

Five individuals involved in planning the ill-fated event were issued jail terms ranging from three years to five and a half years by a court in Baiyin, a city in Gansu province, where the deaths occurred, state news agency Xinhua reported late Friday.

In May 2021, the 100-kilometre (62-mile) cross-country mountain race turned deadly as freezing rain, high winds and hail hit the competitors.

The five defendants were convicted for "organizing a large-scale event that led to a significant safety incident", said Xinhua.

In the provincial capital of Lanzhou, an official was sentenced to four years and 10 months for "dereliction of duty and bribery", and another to three and a half years for "dereliction of duty" alone, Xinhua added.

Long-distance running and other extreme sports have been booming in China in recent years, as the government promotes exercise for all ages, though slipshod organisation has repeatedly caused problems.

The 2021 incident raised questions over why organisers apparently ignored the incoming extreme weather and led to renewed calls for tighter laws surrounding sporting events.

In the wake of the deaths, Beijing's General Administration of Sport announced that events without national safety standards would be suspended, including mountain trail running, wingsuit flying and ultra-long distance running.

AFP

Rescue workers carry a stretcher as they work at the site where extreme cold weather killed participants of ultramarathon race in Baiyin, Gansu province, China May 22, 2021. (AP)

Organisers of deadly 2021 China ultramarathon sentenced to jail