Conor McGregor posted then deleted a tweet insulting the wife of Khabib Nurmagomedov on Tuesday night. McGregor, who lost a highly controversial fight against lightweight champion Nurmagomedov at UFC 229, appears to be angling for a rematch, despite ostensibly entering retirement. 

McGregor tweeted photos taken on Nurmagomedov's wedding day, accompanied by the insult, "Your wife is a towel mate," per MMA Junkie's Simon Samano.

Samano reported McGregor removed the post after it had been live for around 15 minutes. However, Samano also shared a screengrab of the offending post.

McGregor subsequently tweeted a message aimed at Nurmagomedov himself:

Khabib eventually responded, calling McGregor a "rapist," telling him that "justice will find you."

Ali Abdelaziz, who manages Nurmagomedov, had previously responded with an incendiary tweet of his own (Warning: Language NSFW):

"I am aware of the recent social media exchange between Khabib Nurmagomedov and Conor McGregor," UFC president Dana White said in a statement, according to Yahoo Sports' Kevin Iole. "The ongoing situation has escalated to a level that is unacceptable. As such, we are taking the necessary steps to reach out to both athlete camps and this situation is being addressed by all parties internally."

According to Tariq Panja of the New York Times, McGregor is being investigated by Irish police after a woman said he sexually assaulted her in December 2018.

McGregor's words about a rematch represent a fairly transparent attempt to goad Nurmagomedov into a return bout. Yet his willingness to get personal is reminiscent of the unsavoury events when the two met in the Octagon.

McGregor tapped out against Nurmagomedov back in October, prompting an ugly aftermath during which Numagomedov became embroiled in a physical altercation with members of the Irishman's entourage.

Nurmagomedov left the Octagon to engage one member of McGregor's team. The incident earned both fighters fines and suspensions.

Prior to the fight, McGregor had taken aim at his opponent's religious beliefs, his father and his manager's reputation. While McGregor tried to explain it away as "just business," when the two tangled in the Octagon, Nurmagomedov had obviously taken the insults to heart.

These two renewing hostilities is a complex proposal for UFC, not least because McGregor announced his retirement last month. However, Nurmagomedov quickly ridiculed the idea, per the Independent: "I don't think he's finished."

White has also expressed doubts McGregor's retirement will stick, per Chisanga Malata of the Daily Express.

It seems as though McGregor is prepared to do all he can to leverage rematch with Nurmagomedov, even if it means initially walking away from the sport. Sanctioning a second fight would be a risk for White, even if Nurmagomodev agrees.

While there's no doubt the draw would be immensely lucrative, the first fight arguably did more harm than good for UFC.

McGregor's reputation as a trash-talker is well-known and considered entertaining by many. Yet there's no doubt he's crossed the line on multiple occasions.