Videos of fans fighting in Las Vegas have flooded social media after Conor McGregor’s UFC lightweight title fight with Khabib Nurmagomedov descended into a post-fight brawl.

The Russian, who defeated McGregor with a fourth round submission, immediately vaulted the Octagon and attacked the Irishman’s corner and violence spread to the crowds leaving the T-Mobile Arena.

"Pandemonium" ensued outside the main hall, with videos appearing to show a large fight between supporters of the Irish and Russian fighters flooding Twitter and Snapchat.

In one, a man appears to be knocked unconscious before onlookers try to break things up.

In another, a man wearing a yellow T-shirt with an Irish shamrock on the back is seen in an altercation with two men before he and a friend are apparently attacked.

McGregor and Nurmagomedov had earlier been heard trading insults between rounds.

Explaining his actions after the fight, Nurmagomedov, who is a Muslim, said: “This is not my best side. He talked about my religion, my country, my father.”

“I want to change this game. You cannot talk about religions and nations. This for me is very important," he added.

While the Russian fought with McGregor’s trainers, at least two men jumped into the ring to attack the Irishman while he was still recovering on the mat, with one striking him in the back of the head.

UFC president Dana White said that three of Nurmagomedov’s team had been arrested and “were on their way to jail”, adding that the decision not to present the victor with McGregor’s belt in the Octagon had been made for “security reasons”.

Police escorted the two fighters out, with security escorts for their respective entourages.