Is this the incident that sparked McGregor's rampage?

Conor McGregor's violent rampage on a bus full of UFC fighters appears to have stemmed from this altercation a few days earlier.

Before McGregor invaded the media day for UFC 223 in Brooklyn on Thursday, his teammate Artem Lobov was involved in a fiery confrontation with
Khabib Nurmagomedov at their hotel.

The altercation never got physical, but Nurmagomedov could be seen putting his hands on Lobov's face, as you can see in the video above.

McGregor, who has a fierce rivalry with Nurmagomedov, was said to be incensed by the incident with Lobov, and immediately flew to New York in a rage.

McGregor was freed by a New York judge on $US50,000 ($A65,000) bail on Friday after being charged with assault for his part in the violent attack on a bus Nurmagomedov was travelling in.

The UFC's best-known athlete and an international drawcard McGregor, 29, appeared before a judge at the Kings County Criminal Court, dressed in a blue, long-sleeved shirt that hid his trademark tattoos.

He is charged with three counts of assault and one count of criminal mischief.

"He's the most visible face on the planet; he has no criminal history and the bail package is completely appropriate in the $50,000 amount," his lawyer Jim Walden told the judge.

McGregor, sporting a beard and a somber expression, stood through the hearing with hands shackled behind his back, saying only a few inaudible words to the lawyer.

The judge also granted a request to allow to the Irish-born McGregor to travel outside the United States before his next court appearance on June 14.

The MMA star had surrendered to police on Thursday evening, soon after a video of the fracas at Brooklyn's Barclay Center went viral.

It appears to show McGregor and his entourage using a metal barricade and other objects to smash windows on a bus filled with fighters departing from the media event.

UFC president Dana White has said the van attack was "the most disgusting thing that ever happened in the history" of the UFC.

McGregor, who became the first fighter to hold two world titles simultaneously when he beat Eddie Alvarez for the lightweight belt in Manhattan in 2016, has not fought in a UFC bout since the win over Alvarez in November 2016.

He previously told Reuters he made an eye-watering $US140 million ($A196 million) from last August's boxing match with Floyd Mayweather.

with AAP