Actor Hafthór Júlíus Björnsson has once again shown why he plays a character nicknamed "The Mountain" in hit TV series Game of Thrones, breaking a keg toss world record at the World's Strongest Man qualifying event in Sweden.

The 206-centimetre-tall giant, who plays Gregor Clegane in the HBO series, threw the 15-kilogram keg over seven metres into the air, taking first place in the competition and breaking his own record.

"It was easy! I could have broken the roof," the Icelandic 27-year-old said afterwards.

"It was amazing to do this in front of the great crowd. Bring on Europe's Strongest Man."

Björnsson has won the qualifying event for the last two years, and has placed in the top three positions for the competition for the past four years.

He began his career as a strongman after an ankle injury ended his run as a basketball player.

He has since won seven competitions, including Iceland's Strongest Man, Iceland's Strongest Viking and Iceland's Strongest Troll.

He also made headlines earlier this year when he broke a 1,000-year-old Icelandic record, carrying a 650kg log on his back for five steps, breaking a record set by Orm Storlfsson a millennium ago.

Björnsson joined the Game of Thrones cast in 2014 when producers filming in Iceland sought a large man to carry on the previously cameo role of Clegane.