Hafþór Júlíus Björnsson claims he spat at Eddie Hall during their tense confrontation.
The long time rivals are set to go toe-to-toe in their long-awaited boxing match in Dubai this weekend.
And things got very heated indeed when the pair crossed paths – totally unexpectedly – in the gym on Sunday (13 March).
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In a video shared online, Hall, 34, squares up to Thor, threatening to 'bite his nose off' if he touches him.
The pair then begin pushing one another before people manage to get in between them and pull them apart, with Hall telling the Game of Thrones star to 'step outside'.
As he gets ushered out the door, Hall then appears to spit at Thor, 33, who returns fire with his own salty projectile.
Speaking about the incident, Thor said he wasn't proud of what happened, but said the adrenaline got the better of him.
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In a video to his YouTube channel, he wrote: "I am getting a lot of questions regarding an incident that occurred between Eddie and I yesterday.
"I was getting ready to train when i received a message letting me know that Eddie was five minutes away. I had no idea that this was happening, it was an obvious setup that Eddie was in on.
"Things got pretty heated, insults were thrown and it ended with Eddie being dragged out of the building, severely injuring someone involved, whilst trying to spit on me.
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"I did spit back, not my finest moment but the adrenaline was cranked and I was shocked that he would do something so disgusting.
"Regardless, I managed to keep quite calm, all things considered, as I didn't want to throw two years of hard work out the window.
"I'm looking forward to stepping into the ring with Eddie on Saturday so we can settle this once and for all, without it turning into a disgusting street fight which is clearly what Eddie wanted after his clear lack of discipline in yesterday's display."
Last week, fans were praising Thor for his impressive transformation ahead of his fight with Hall.
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Much has been made of both men's dedication, with Thor going from eating 10,000 calories a day to just 4,000, losing more than 50kg in the process, and Hall losing a fair bit of weight himself.
But it's not just changes to his physique that have impressed people.
After sharing a recent video from his training camp, fans have shared their admiration for The Mountain's impressive boxing skills.
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In the video, he can be seen sparring with another fighter, moving pretty quickly around the ring and landing some big punches.
Commenting on the video, one user said: "Love seeing someone that was sooo big and strong go to boxing and actually learn to be technical and develop great movement.
"If you kept on I believe you could go really far in boxing. Stay moving and keep a high pace on Eddie and I see this being a hard night for Eddie. Can’t wait!!!"
You can watch the fight on Saturday 19 March, with the fight streamed for free via SEGI.TV.
Topics: Eddie Hall, Boxing, Sport, UK News