UFC star Conor McGregor's life is said to be in danger after clashing with a deadly Irish crime gang who could drag him "down into the cesspit".

McGregor, who hails from Dublin, is alleged to have "inadvertently locked horns with members of the Kinahan cartel, which includes people who are well accustomed to killing," according to respected crime reporter Paul Williams of the Irish Independent.

Williams said nobody should underestimate or play down the serious and perilous situation that McGregor is in after reports the infamous Kinahan crime cartel want to seek retribution against the UFC lightweight champion over an assault in an Irish bar.

USA TODAY Conor McGregor fought Floyd Mayweather Jr in August.

One of the men McGregor punched in the bar fight is believed to be a close associate of convicted Irish drug dealer Graham 'The Wig' Whelan.

READ MORE: Mayweather 'training' for ring return

Williams told Irish radio station Newstalk Breakfast that McGregor is in a "very dangerous place at the moment" and understands the 29-year-old will be approached in the next 48 hours to be given a GIM form, a Garda Information Message from the Kinahans that tells him there may be a threat to his safety.

GETTY IMAGES McGregor holding a bottle of whiskey while speaking a the post-fight press conference following his loss to Mayweather.

"He has come into conflict through probably no fault of his own, with a group of very, very dangerous people who are tied up with the Kinahans," Williams said.

"These people do not care who Conor McGregor is, what he stands for, how powerful he is, they will drag him down into the cesspit."

Williams believes McGregor's predicament is a huge story and that he's in potentially very serious danger.

"He has ended up crossing swords - accidentally or however - with some very, very heavy people, or some people who are related to some very, very heavy people who could pose a very serious threat to his safety, and potentially his life. And I don't say that lightly," he said.

"These people, you have to remember – as I keep saying – they don't care, they don't have parameters, they don't have boundaries, they don't discriminate between whether you're an international sporting icon or just a man on the street.

"They shoot you, they injure you, they do whatever they want to do."

McGregor's last professional fight was when he fought and lost to Floyd Mayweather in the 10th round of their boxing match in Las Vegas in August.