Hundreds attend paddle-out tribute for murdered Perth brothers Jake and Callum Robinson

• Two Aussie brothers were shot dead in Mexico 
• They were on a surfing trip with their US friend 
• READ MORE: Farewell service for Jake and Callum Robinson 

Hundreds of mourners have held a 'paddle-out' to pay tribute to two Perth brothers who were killed in Mexico.

Callum Robinson, 33, and his brother Jake, 30, were travelling with their American friend Carter Rhoad, 30, on a surfing trip in the Mexican state of Baja California in April when they failed to check into their accommodation.

A few days later police arrived at their last known whereabouts and found a campsite with traces of blood.

The three bodies were later discovered in a well, with bullet wounds to the head.

The paddle-out on Saturday was held a week after a moving memorial service at Sacred Heart College in Sorrento where the boys graduated high school. 

Two large portraits of the brothers sat on the sand at Sorrento Beach on Saturday as surfers formed a ring in the water.

The boys father Martin Robinson said a few words in the centre of the group as two wreaths were laid in the water.

The surfers and kayakers then made their way back to shore where they were embraced by dozens more on the sand. 

Australian Federal Police are working with Mexican authorities to bring justice for two murdered brothers.

Foreign Minister Penny Wong said Australia's embassy in Mexico would continue to work with federal police and local authorities.

'I am heartbroken for Jake and Callum's parents and am thinking of them at this incredibly difficult time,' she told AAP.

Parents of the slain Australians, Debra and Martin Robinson, said the world had since become a darker place and were preparing to bring home the bodies of their sons.

Mexican prosecutors have identified three suspects - two were caught with methamphetamine and one had one of the victim's phones - but it's believed more people may have been involved.

A criminal charge of forced disappearance, equivalent to kidnapping, has been laid against the accused ringleader.

The man, Jesus Gerardo, has a criminal record of drug dealing, vehicle theft and domestic violence.

The AFP has a presence in Mexico and is liaising with local authorities.