Irish-born mixed martial arts star Conor McGregor has been charged with three counts of assault and one count of criminal mischief.

A New York judge freed McGregor, 29, on $US50,000 ($A65,000) bail on Saturday (Friday local time) after he was charged for his part in an violent attack at a media event to promote UFC 223.

“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.

The MMA star surrendered to police on Friday (Thursday evening local time), soon after a video of the fracas at Brooklyn’s Barclay Center went viral.

It shows 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.

The sport’s best-known athlete and an international drawcard, McGregor appeared in Kings County Criminal Court dressed in a blue, long-sleeve shirt that hid his trademark tattoos.

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

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

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 that win in November 2016.

He previously boasted to Reuters that he made an eye-watering $US140 million ($A196 million) from last August’s boxing match with Floyd Mayweather, which he lost.

McGregor will be allowed to travel outside the United States before his next court appearance on June 14.

-with AAP