The three men were killed during a camping and surfing trip along Mexico’s Pacific coast.

Mexican authorities have confirmed the deaths of an American and two Australians who went missing in northern Mexico last week after the tourists’ parents identified their bodies.

The bodies of Australian brothers Callum and Jake Robinson as well as their friend, United States citizen Carter Rhoad, were found at the bottom of a well in the state of Baja California after a days-long search.

All three were in their early 30s and had been shot in the head.

“The victims’ relatives were able to identify them without the need for genetic tests,” a statement from the state prosecutor’s office said.

The three men went missing while on a surfing holiday near the popular tourist town of Ensenada, about 90 minutes south of the US-Mexico border on the Pacific coast.

They are believed to have been killed after resisting an attempt to steal their pick-up truck, state prosecutor Maria Elena Andrade Ramírez said at a news conference.

The vehicle, which had been set on fire, was found nearby.

Australian Treasurer Jim Chalmers expressed sympathy for the Robinson family. “I think the whole country’s heart goes out to all of their loved ones. It has been an absolutely horrendous, absolutely horrific ordeal and our thoughts are with all of them today,” he said.

Three suspects, two men and one woman, have been arrested on suspicion of involvement in the case.

One of those arrested has a history of violence, drug dealing and robbery, officials said.

Investigators said earlier that the bodies were recovered from a well about 50 feet (15 metres) deep in an “advanced state of decomposition.”

Another corpse found at the site had been there longer and was unconnected to the others, officials said.

The three surfers were last seen on April 27 and reported missing a couple of days later, when authorities launched a multi-day search with the help from the US’s Federal Bureau of Investigation (FBI).

Baja California, one of Mexico’s most violent states because of organised crime gangs, is also known for its inviting beaches and the Ensenada area is considered among its safer parts.

At the news conference, Andrade Ramírez was questioned by one reporter who expressed approval that such a massive and rapid search was mounted for the foreigners, but asked why, when local people disappear in the area, it took weeks, months, or even years for action to be taken.

“Do you have to be a foreigner in Baja California in order for there to be an investigation if something happens to you?′ asked the reporter, who did not identify herself by name. ”Every investigation is different,” Andrade Ramírez replied.

As if to underscore that point, dozens of mourners, surfers and demonstrators gathered on Sunday in Ensenada to pay their respects to the surfers and voice their anger over the deaths.

“Ensenada is a mass grave,” read one placard carried by protesters.

Many marched with their boards scrawled with messages, including “beaches, security, freedom, peace”, “no more deaths” and “Australia, we are with you”.