Bones found on the NSW mid-north coast are believed to be those of French backpacker Erwan Ferrieux, who was last seen in February.

Mr Ferrieux, 21 and 20-year-old British tourist Hugo Palmer have not been seen since passers-by discovered their belongings at Shelly Beach near Port Macquarie.

Their rental car was found in a nearby car park, with other belongings – including travel documents – still inside.

A ground and water search involving police divers, Marine Rescue and SES failed to find the pair.

A human bone was found in the water at nearby Flynns Beach on June 15. Two days later, two more bones were found in the water at nearby Flat Rock.

DNA testing indicated the three bones belonged to Mr Ferrieux, police said on Monday.

“DNA comparison of the three bones located in June have confirmed that they did come from the same male person,” Superintendent Paul Fehon said in Port Macquarie on Monday.

“We believe from the DNA comparisons that it belongs to Erwan Ferrieux.”

Police are investigating if a small human bone found by passers-by on Sunday afternoon at Flynns Beach also belongs to Mr Ferrieux. It will be subject to forensic analysis.

Mr Palmer, an Englishman, and Mr Ferrieux, a Frenchman, have been close friends for years, according to their Facebook pages.

They both appear to have attended Sackville School, south of London.

-AAP