It was a case of "ambition getting mixed up with capability" that saw five riders hospitalised during an off-road rally south of Darwin, an event spokesperson has said.

On Saturday the CareFlight Top End Rescue Helicopter and Air Ambulance were twice called to the KTM Australia Adventure Rallye at Maryfield Station, about 500 kilometres south of Darwin,

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In the first collision, one man sustained pelvic injuries while the other received, chest, shoulder and leg injuries.

After transferring the patients to Katherine, who were then taken to the Royal Darwin Hospital by plane, the helicopter returned to the station to help four more injured riders.

Three men were transferred to the Darwin hospital, while one with minor injuries continued riding.

Two of the men were discharged on Sunday.

The other three remain in hospital in a stable condition.

Ambition 'mixed up with capabilities'

Communications director at Automative Holdings Group David Christison spoke to the ABC on behalf of race organisers KTM Australia, and said he believed dusty conditions had played a role in the crashes.

"I think it's fair to say that while there was a very comprehensive emergency management plan, a very strong medical response plan, and even a critical incident plan, some of the guys simply got their ambitions mixed up with their capabilities," Mr Christison said.

"As I understand it some tried to overtake other riders in very dusty conditions and came to grief.

"At no stage was anybody else in any danger."

But he acknowledged not all of the injured riders had been in the wrong.

"Where two bikes come together, obviously one is the victim and one is involved in an act that probably shouldn't have been," he said.

"But the point is all these guys are heading in the same direction and if somebody falls victim to somebody else's careless riding then that is unfortunate, but as I say, there's nothing sinister about it."

He said "strict further rules" had been brought in following the crashes: "Don't overtake people in dusty conditions and don't ride beyond your capabilities".

On the KTM Australia home page it says the rally "is tailored to suit all rider abilities", and Mr Christison was asked whether it was wise to have riders of varied ability on the same course.

He declined to answer directly, instead stating it was "a very, very well organised event".

Two doctors, three paramedics, a flight nurse, a helicopter, a fixed wing aircraft were all provided by the race organisers.

CareFlight was on standby for the first two days, and the Royal Flying Doctor service was to be engaged for the final stages.

Mr Christison also said riders were given full rider packs, full details of the conditions, menus for each nights dinner, transport and logistics, sleeping arrangements and end of trip arrangements before heading into the race.

He believed each rider bore personal responsibility for their insurance, but was not sure if they were required to prove they had insurance before entering.

"It was a very well organised event. 272 people were not hurt," he said.

"In motorcycle rallies around the world there are riding incidents, just as there are on the road every day."

David Christison said the race was "very well organised". ( KTM Australia / Wilkinson Photography )

'Alarmed' by accident rate

CareFlight general manager Craig Gibbons said he had been in touch with rally organisers because he was "naturally a little bit alarmed with the accident rate".

"They do have a well-written critical incident management plan that they've been following but I don't think anyone expected this number of casualties," Mr Gibbons said.

"We weren't called out yesterday, the second day, so I hope that trend continues."

The off-road motorbike rally will hold events at Humbert River, Limbunya and Gregory National Park during the coming days before rolling into Alice Springs for the start of the 2018 Tatts Finke Desert Race.