UFC lightweight champion Conor McGregor is reportedly in serious danger with the Kinahan cartel after being involved in a brawl, according to an Irish crime reporter.

The 29-year-old was allegedly involved in a pub brawl at the Black Forge Inn in Crumlin on Sunday (26 November) that reportedly saw him punch the middle-aged relative of a senior member of the Kinahan drug cartel.

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Without mentioning his name, various publications have since run stories about a well-known Irish celebrity being involved in the brawl. McGregor later hinted that it was him by posting a video on Instagram with a caption that read "The celebrity".

McGregor is said to have assaulted a young man before attacking the relative, first identified as an associate of the cartel, who stepped in among the fracas.

Police stated later that they were aware of the allegations but no complaints have been made following the incident.

The "Notorious" is now in serious danger according to Irish crime reporter Paul Williams in light of the Kinahan cartel now reportedly demanding €900,000 (£790,000, $1.06m) in protection money from the combat star or risk getting murdered.

"I have to say about this, and I'm wearing my old, veteran crime reporter hat. Conor McGregor is in a very dangerous place at the moment," Williams told Newstalk Breakfast on Thursday morning (29 November). "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.

"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. I would say, in the next 48 hours, if he still in the country — and I understand that he may have left the country — but if he is still in the country, I understand from my sources that the Garda will be approaching him to give him a GIM form, which is a Garda Information Message, to tell him that there may be threats to his safety.

"This is a huge story, and imagine what it would do to our reputation if this national sporting icon is attacked by a bunch of gangsters."

The celebrity A post shared by Conor McGregor Official (@thenotoriousmma) on Nov 27, 2017 at 8:43pm PST

McGregor's father Tony, however, has rubbished all the reports and rumours, claiming his family has nothing to fear from anyone.

"That's all nonsense, that is. Absolute nonsense. It's an absolute nonsense story," he told the Irish Mirror. "It's grown legs and it's getting that ridiculous – it's become funny."

"We have nothing to fear here whatsoever. There's no one after us for anything. We're a law-abiding family and we've stayed a law-abiding family."

The Kinahan cartel is believed to be the biggest importer of cocaine in Ireland according to the Daily Mail and is currently involved in a feud with its rivals, the Hutch gang.