IF you thought the two miles of the Melbourne Cup was a grueling test of stamina for the top stayers, spare a though for those that contested what has been billed ‘the world’s longest horse race’ in Mongolia.

Agence France-Presse reports that more than two dozen horsemen raced across the finish line in Mongolia after a test of endurance that would have impressed even Genghis Khan.

The international group of riders pounded 860km across the Asian country's vast grasslands in the 10-day Mongol Derby, which organizers call the world's longest horse race.

South African architect Charles van Wyk, 28, tied for first with local rider Shiravsambuu Galbadrakh, leading home a field from 10 countries including Argentina, Australia, Britain, New Zealand, Spain and the United States.

The Adventurists, a British organization that dreamed up the Derby, designed the race as a way to promote Mongolian tradition and culture, while raising money for charity.

Participants changed steeds every 40km or so at urtuu, relay stations patterned on those used during Genghis Khan's time to deliver post across the Mongol empire, from the Pacific Ocean to the edge of Europe.

“Modern life is changing the steppes but that does not mean they are all coming to the city,” Van Wyk said. “In fact the quality of life is quite good on the steppe and even the foreign riders longed to go back after we returned to the city.”

Nomads in traditional ger, a round felt tent, manned each station, providing riders with boiled mutton and fermented mare's milk, a common drink in Mongolia. But on some nights, they slept in the open.

“There were days when I wondered why I had even started this race because I was so tired. But then I would get back into the rhythm of things and press on,” Van Wyk said.

A total of about 700 horses were used during the event.

“Having been in Mongolia for the past seven years we came to understand how important horses are to the local culture,” Adventurists founder Tom Morgan said. “There is nowhere else in the world with so many horses and so much space, so it seemed like the perfect place to do it.”

The Adventurists also organize the annual Mongol rally, a race from London to Ulan Bator in dangerously small vehicles, but Morgan said he experienced a nervous moment when the horse riders had set off.

“There was a lot of apprehension because we had never done anything like this before. But in the end it was a great success, thanks largely to the great network of nomads in Mongolia, and some really good horses,” he said.

The riders emerged relatively unscathed from the marathon ride, with only a few scrapes and bruises and one minor concussion. That result surprised horse trainer Yundenbat Unenburen, who helped set up urtuu for the Derby.

“I didn't think they would even get halfway. But when they all crossed the finish line I had to admit I was wrong. They proved that they are the bravest, hardest and toughest people,” Unenburen said.

Every competitor was handed a special tablet modelled after those used by ancient urtuu riders, which allowed them free access across the empire.