A gang of Mexican highway robbers dressed as police pulled Australian surfers Dean Lucas and Adam Coleman over, executed them and doused their bodies in petrol before setting them alight.

That’s the horrifying scenario Mexican authorities alleged on Friday after announcing three of the five robbers had been arrested.

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DNA tests on two badly-burned bodies found in Mr Coleman’s Chevy van should be completed in the next week to confirm if the two men did meet such a gruesome end.

“These people are part of a criminal group dedicated to vehicle thefts, drug dealing and with a history of committing murders,” Marco Antonio Higuera Gomez, chief prosecutor of the crime-ridden Mexican state of Sinaloa, told reporters.

Julio Cesar Muniz, Martin Rogelio Muniz and Sergio Simon Benitez were arrested in recent days and a manhunt continues for the two other men.

Mexican authorities displayed a large collection of firearms, numerous electronic devices including laptops stolen by the bandits, police uniforms, masks and more than 100 packets of crystal meth netted following the arrests.

In the early hours of November 21 the gang had allegedly staked out a section of the Benito Juarez Highway, described by a local mayor as a “Bermuda Triangle” for its violent crimes.

Mexican authorities inspect the burnt out van.

Mr Coleman and Mr Lucas, both 33 and from Perth, were heading south to the city of Guadalajara to visit Mr Coleman’s Mexican girlfriend.

One of the gang members working as a spotter notified the others the Australians’ van could be a target, they drove up in a Jeep Cherokee, flashed blue lights and pulled them over, Mr Higuera alleged.

Guns were allegedly pulled on the Australians and when one of the gang members attempted to get into the van Mr Coleman fought him off and was shot in the face.

Mr Lucas was also executed.

The van was driven to a rural area with the bodies inside and set alight.

Mr Lucas, who was planning to propose to his English girlfriend, and Mr Coleman, known for his love of life and wild dreadlocks, were experienced travellers, spoke Spanish and had been living in Edmonton, Canada.

They drove the distinctive blue and white Chevy from Canada, surfing along the way.

Their heartbroken parents in Australia have submitted DNA to be matched against the profiles taken from the bodies found in the van.

– AAP