Arman Tsarukyan headbutted Dan Hooker at the ceremonial weigh-ins in a shock moment ahead of their main-event bout.
A UFC lightweight title eliminator between Tsarukyan and Hooker headlines the promotion's first trip to Qatar.
The Armenian could earn a shot against UFC lightweight champion Ilia Topuria if he beats the Kiwi veteran, who is looking to improve his three-fight winning streak.
Both fighters made weight at Friday's official weigh-ins, with Tsarukyan scaling at 156lbs while Hooker weighed in at 155.5lbs.
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They faced off for the final time ahead of Saturday's main-event bout and it almost kicked off.
After Tsarukyan tipped the scales, he approached Hooker before headbutting his rival.
UFC matchmaker Mick Maynard immediately intervened as security pulled both fighters away.
Hooker laughed as he was pulled away from Tsarukyan.
They exchanged words on stage before talking to Michael Bisping
Hooker said: "Let's go. I love it, I love it. Bring it on!"
Tsarukyan added: "I'm going to show (a) great knockout and going to get my title (shot) next."
Despite Tsarukyan's headbutt, he likely won't face any punishment given these kinds of acts happen from time to time.
Had Hooker suffered an injury from his opponent's headbutt, then it would have been a different situation.
UFC CEO Dana White shared footage of the incident between Tsarukyan and Hooker on social media, seemingly suggesting he isn't bothered by the headbutt.
Why did Arman Tsarukyan headbutt Dan Hooker?
The clash between Tsarukyan and Hooker has been intensified following the latter's stinging comments ahead of their showdown.
Hooker labelled Tsarukyan a 'rich little spoiled kid' and slammed his foe's decision to withdraw from his title fight against Islam Makhachev at UFC 311 in January.
“I feel like we just come from different places," he explained. "I feel like he’s just a rich little spoiled kid and he acts like that. Pulling out of a title fight the day before and people have seen my career.
"They’ve seen me take the knocks. They’ve seen me pick myself back up. They’ve seen me just tough it out and come from nothing, the first New Zealand based fighter to make it to the UFC. Look at it now, we’ve been able to grind something out."
Tsarukyan, who beat Charles Oliveira in his last appearance, hasn't fought since withdrawing from his scheduled bout against Makhachev.
As for Hooker, he's coming off a win over Mateusz Gamrot at UFC 305 last year.
Topics: UFC
Nasir Jabbar