Three bodies found in a well in Mexico's north-west, believed to be those of two Australian brothers and an American, all had bullet wounds to the heads, police have said.

Officials confirmed the bodies found in a well last week in Mexico belonged to three missing surfers and that they each had bullet wounds.

The site where the bodies were discovered near the township of Santo Tomás was near the remote seaside area where the missing men's tents and truck were found Thursday on a remote stretch of coast.