The disappearances of three backpackers on the NSW east coast could be the work of a serial killer, according to a leading forensic psychologist.

Tim Watson-Munro believes a link between the disappearance of English backpacker Hugo Palmer, 20, Frenchman Erwan Ferrieux, 21, and missing Belgian Theo Hayez, 18, can’t be ruled out.

Watch the video above.

"I don’t want to be hysterical about it but you have three foreign backpackers who have disappeared off the eastern seaboard of Australia, 300 kilometres apart, in very mysterious circumstances," Watson-Munro told The Latest on Wednesday.

"It’s a bit too cute to say they all drowned. It’s a huge coincidence if that's the case."

Bones found on the NSW mid-north coast are believed to be those of backpacker Erwan Ferrieux (L). Credit: AAP

Ferrieux and Palmer went missing from Shelly Beach near Port Macquarie in February 18. Though it is believed the pair drowned in rough surf, their bodies have not been found.

Their rental car was found in a carpark near the beach, with their travel documents still inside.

Last week, Bones found washed up on nearby Flynns Beach in June were confirmed to be that of Ferrieux.

Police are yet to find any trace of Palmer.

Hugo Palmer and Erwan Ferrieux were both reported missing in February. Credit: Instagram

Months later and more than 300 kilometres away, Hayez was last seen leaving a Byron Bay bar on May 31.

The 18-year-old was spotted on CCTV walking through the popular beach town after leaving the Cheeky Monkey's bar at about 11pm.

He was reported missing days later, triggering a massive police search of the area.

His belongings, including his passport, were left untouched at the hostel where he had been staying.

Theo Hayez went missing after visiting a Bryon Bay bar. Credit: Twitter

No trace of him has been found despite the continued efforts of locals and his family - who traveled from Belgium to join the search.

Watson-Munro believes police should investigate the possible link between the three more thoroughly.

RELATED:

"Given the coincidence of three people disappearing in such a short period of time, similar profiles, very vulnerable as people are visiting Australia as backpackers. I think it’ll be amiss to not investigate this more thoroughly," he said.

"I think they’ve got as much information as we all do and it's a matter of interpreting that information.

"The facts of the case are that we have three missing people from overseas who have disappeared within a close proximal range of one another in mysterious circumstances. That’s all I can say and, frankly, that’s all they can say."

The teenager (right) was seen at a bottle shop earlier on May 31. Credit: NSW Police

NSW Police said there are no definitive links between the cases of the three backpackers and there is no indication of foul play.

But Watson-Munro says that response is expected from authorities to prevent causing panic in the community.

"I don’t think they want to alarm people," he said.

"Nobody wants to think there’s a serial killer patrolling the Pacific Highway looking for victims and I hope that I’m wrong but it may well be the case that I’m right."

- With AAP