An Australian man and his girlfriend have been found dead in Canada, in what local authorities are treating as a double homicide.

On Monday the bodies of Lucas Fowler, 23, and Chynna Deese, 24, were found on the side of a remote stretch of Alaska Highway in British Columbia.

Fowler, from Sydney’s north shore, and Deese, from the US state of North Carolina, were about to travel around the “top half of the globe” before their lives were cut short.

NSW Police confirmed the news on Friday, with a statement from Fowler’s family that read: “We have lost our dear Lucas Fowler, son, brother, grandson and friend, in the most terrible of circumstances. To lose someone so young and vibrant, who was travelling the world and just enjoying life to the full, is devastating.”

"To know his beautiful girlfriend, Chynna Deese of Charlotte, North Carolina also lost her life in this violent event is too cruel. All our love and best wishes go to Chynna's family and friends.

"We are all now travelling to Canada to be with our boy and to bring him home.

"Our deepest thanks for all your love and care. At this stage we can only move forward a minute at a time, and those minutes are moving so slowly."

In a press conference on Friday afternoon, Sgt. Janelle Shoihet of the Royal Canadian Mounted Police said it is too soon to tell if the victims were targeted, or if their murders were a "crime of opportunity".

An eyewitness told local news outlets she saw a couple that matched the description of Lucas and Chynna while driving on the Alaska Highway on Sunday afternoon.

"We just saw their van on the side of the road and we saw a young couple, and the van hood was up like it had broken down, and they were sitting in some lawn chairs in the ditch," she said.

She said she didn't approach, due to safety concerns, but notified local authorities.

The area the Australian man and his American girlfriend were found is called Highway 16, but is commonly known as the "Highway of Tears".

Since 1970, up to 50 women (mostly Indigenous Canadians) have been murdered or have disappeared on this 724 kilometre stretch of the highway in British Columbia.

Along the road there are warnings not to hitchhike for fears a serial killer lives in the area.

In 2015, the Canadian Government launched a national inquiry into a national inquest into the death of Canada's Aboriginal women, of which the Highway of Tears was a part.