Dakar Rally leader Aleš Loprais has withdrawn from the race after hitting an Italian spectator, who later died.

Loprais — who was leading the truck category — came over a sand dune in the Saudi Arabian desert and his vehicle knocked over a spectator, identified by organisers as Livio Sassinotti, who was standing on the other side of the dune.

Footage of the incident appears to show Sassinotti conscious immediately after the contact, but Loprais said the man suffered a heart attack on the way to the hospital.

"He was injured, he felt nauseous after two to three hours and he had a heart attack while being transported to the hospital," the 43-year-old said in a video on his Facebook page.

The accident occurred during Tuesday's ninth stage, but Loprais said he was unaware of it until after his arrival at the bivouac that night, when stewards showed his team the footage.

Loprais said on his Facebook page that the 69-year-old man was taking photographs on the downslope of the dune.

"One human life has ended, indirectly my fault because I was driving," Loprais said.

"I have to admit that me and my crew didn't know about it at all. We've got onboard [cameras] and other videos that prove it, but nothing changes that a human life ended … unfortunately, he was standing under the dune and we didn't see him at all.

Sassinotti is not visible in the footage from inside the truck's high cab.

Organisers said Loprais was devastated and supporting local authorities with their inquiry.

"The rally organisers join him in offering their condolences to the family and friends of the spectator, Livio Sassinotti," they said in a statement.

Reuters/ABC