A couple has been shot dead on a Canadian highway where it dozens of women have been murdered or vanished.

Australian Lucas Fowler, 23, and his American girlfriend, Chynna Deese, 24, were driving in a Blue 1986 Chevrolet van towards a cattle ranch in British Columbia when they were killed.

Witnesses claim their car broke down on the side of Alaska Highway. That is the last time they were seen alive.

Their bodies were found around 20km from the popular Liard Hot Springs.

NSW Assistant Commissioner Mark Jones said in a press conference that both had been shot in 'horrific circumstances'.

Police believe their deaths are not linked to any other active or ongoing investigation.

Their bodies were found around 20km from the popular Liard Hot Springs
Chynna and her brother

Lucas' father Stephen Fowler, the chief inspector for Australia's NSW Hills District, and homicide officers are travelling to Canada to provide support to the grieving family.

Mr Fowler said in a statement: "To lose someone so young and vibrant, who was travelling the world and just enjoying life to the full, is devastating."

The Royal Canadian Mounted Police are investigating the incident and leading the hunt for the killer.

Local police also appealed for assistance from anyone who might have dashcam video and drove past the blue van with Alberta plates, Daily Mail reports.

They were driving a blue Chevrolet van
Lucas Fowler and his girlfriend Chynna Deese were both shot dead

A Canadian couple - Sandra and Curtis Broughton - claimed they had spoken to Lucas and Chynna and stopped to help after seeing their blue van had broken down.

They were heading home to Fort Nelson and stopped to help the couple about 3:30pm on Sunday.

The couple were travelling down a 720-km stretch of a road known as 'The Highway of Tears'.

Mrs Broughton told the media: "An engine problem, the engine was flooded, the one cylinder wasn't working. He was quite confident it would be okay.

"We did see if they needed our help and he said not, he was okay."

They were shot dead on the side of the Alaska Highway (
Image:
CBC News)

There were reports indicating between 18 and 50 women have disappeared or have been killed on the highway since 1970.

The couple's death has sparked fears of a serial killer but police refuted these claims on Saturday, saying their murders were 'unique'.

Chynna's father, Dwayne, told the Charlotte Observer that he does not believe it is a serial killer either.

Both families have paid tributes to their children as the Fowler family said they lost Lucas in 'the most terrible circumstances' and the Deese family said they were 'in shock and heartbroken'.