Floyd Mayweather Jr says Conor McGregor should show more class and be a "gentleman" outside the ring after his rival was arrested this week.

Former UFC champion McGregor was charged with three counts of assault and one count of criminal mischief following an alleged attack on a bus full of rival fighters in Brooklyn on Thursday.

The Irishman's bail was set at $50,000 during his arraignment hearing at Brooklyn Criminal Court on Friday and he is due back in court on June 14.

Legendary boxer Mayweather, who came out of retirement to beat McGregor last year, took a dig at his foe during a Showtime broadcast.

He said: "I feel that when you have reached such high status, you have to carry yourself in a classy way.

"Outside the ring, you have to carry yourself as a gentleman."

Mayweather last month said he will apply for an MMA licence and the American said a shot at UFC is still in his thoughts.

"Retirement has been great but as you know and everyone knows, I go in retirement and I come back. It is possible I do come back, but if I do come back, it has to be in the octagon," he added.