Callum and Jake Robinson, both in their 30s, are believed to have disappeared while on a surfing and camping trip in the Baja California region near Ensenada.

They have not been heard from for five days.

Photos from Mexico, shared by friends online, show the trio’s abandoned ute parked atop an oceanside cliff.

Their mother Debra Robinson has taken to social media to appeal for help.

Posting to an Ensenada Facebook community group, she wrote: “Reaching out to anyone who has seen my two sons.”

“They have not contacted us since Saturday 27th April.

“They are travelling with another friend — an American citizen — (and) were due to book into an Airbnb in Rosarito after their camping weekend but they did not show up.

“Callum is a type one diabetic so there is also a medical concern.”

Another friend said Callum was due back at work in San Diego and flags were raised when he did not show up.

The trio were supposed to be surfing at a spot called ‘k28’, friends said.

The Robinsons’ American friend, Carter Rhoads, is also missing.

Ms Robinson said the trio were travelling in a Chevrolet Colorado ute with Californian number plates reading 7018W1.

Friends have also spread the word on Mexican social media pages revealing the three men were on a surf trip.

“My Australian friends Jake and Callum Robinson have gone missing around Rosarita/Ensenada region of Baja California Norte Saturday morning,” one post said.

“Callum is a diabetic — this is a very dire situation if you can please share if you know anyone who lives locally.”

It is understood that Callum had been living in the US, and Jake had travelled there to visit him.

The Mexican government’s travel advisory has the area the three men were last seen listed as: “Exercise Increased Caution”

“Exercise increased caution due to crime. Criminal activity and violence may occur throughout the state,” it read.

A Special Operations Group, along with local authorities, have been tasked to search for the missing men.