Arnold Schwarzenneger's 'right hand man' passes away aged 78

Arnold Schwarzenneger and Franco Columbu. Photo / Supplied

Arnold Schwarzenneger has paid tribute to his best friend Franco Columbu, a former two-time Mr Olympia, who died in Italy aged 78.

Columbu was a legend in the strength sports industry as he competed in body building, powerlifting and strongman competitions, reports News.com.au.

He twice won the Mr. Olympia contest in 1976 and 1981 and built a close friendship with Schwarzenneger over the years.

Reports out of Italy state the former strongman champion lost his life in an incident at sea in Sardinia, Italy.

Schwarzenneger often referred to Columbu as the strongest man he ever knew, with the two men building a friendship after first meeting in Munich 54 years ago.

He appeared alongside Schwarzenneger in blockbuster movies "The Terminator", "The Running Man" and "Conan the Barbarian".

The movie star and former Governor of California paid tribute to his best friend in a touching post on social media and with a moving tribute on website medium.

"I love you Franco. I will always remember the joy you brought to my life, the advices you gave me, and the twinkle in your eye that never disappeared. You were my best friend," Schwarzenneger tweeted.

Fellow actor Sylvester Stallone paid tribute to Columbu and posted several images of the two men together.

FRANCO COLUMBU , The greatest and strongest bodybuilder I have ever met has passed... He taught me many things that I have applied throughout my life - We will NEVER HAVE A MAN LIKE THIS AGAIN - thank you for the memories Franco pic.twitter.com/vJgzlI4Jyk

— Sylvester Stallone (@TheSlyStallone) August 30, 2019

"From the minute we met in Munich, you were my partner in crime. We pushed each other, we competed with each other, and we laughed at every moment along the way," Schwarzenneger wrote.

"When I finally got to America, I was alone. I'd left my family, my country, my whole life behind. So when I asked Joe Weider to bring you to train with me, it was because I knew I wasn't the same without my best friend. I could thrive without money, without my parents, but I couldn't thrive without you.

"I am devastated today. But I am also so, so grateful for the 54 years of friendship and joy we shared.

"I love you Franco. I will always remember the joy you brought to my life, the advices you gave me, and the twinkle in your eye that never disappeared. You were my best friend."