Former UFC champion Conor McGregor might have announced his retirement from the sport last week, but that hasn't kept him from lobbing insults at a former competitor in the Octagon.

On Tuesday night, McGregor took shots at the wife of his last opponent, Khabib Nurmagomedov, on Twitter, saying, "Your wife is a towel mate," while posting two photos of Nurmagomedov and his wife on their wedding day. In the pictures, Nurmagomedov's wife's face is veiled.

He later deleted the tweet, which was captured by MMA Junkie on Tuesday night.

Nurmagomedov, who has made a concerted effort to keep his wife's identity private throughout his career, fired back on Wednesday via Twitter calling McGregor a "rapist" and a "hypocrite," likely in reference to the fact that McGregor is reportedly being investigated for an alleged sexual assault in December in his native Ireland, according to The New York Times. In January, McGregor was arrested and released after being questioned in the matter but has not been formally charged with a crime.

The online beef didn't go unnoticed by UFC president Dana White who, in a statement issued Wednesday, called the exchange "unacceptable."

"I am aware of the recent social media exchange between Khabib Nurmagomedov and Conor McGregor," White said. "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."

McGregor also took a shot at Nurmagomedov himself, saying he might be afraid of a rematch. Of course, McGregor is the one who is retired -- although many around the UFC have stated in the past few days they don't believe McGregor's retirement is actually going to stick.

McGregor took to Twitter again Wednesday night, expressing his desire to "move forward, with my fans of all faiths and all backgrounds."

I want to move forward, with my fans of all faiths and all backgrounds.

All faiths challenge us to be our best selves.

It is one world and one for all ❤️

Now see you in the Octagon. — Conor McGregor (@TheNotoriousMMA) April 4, 2019

McGregor and Nurmagomedov fought at UFC 229 in October -- a fight Nurmagomedov won by fourth-round submission -- and then engaged in a brawl after the fight that left both fighters suspended and fined. McGregor's suspension will expire on Saturday. Nurmagomedov's suspension runs through Oct. 6.

McGregor's social media posts led lightweight contender Tony Ferguson to jump into the fray, telling McGregor in a tweet, "You talk to much kiddo. Shhh."

Earlier in the day, Nurmagomedov was speaking at a university in Moscow and said, "I don't think he's finished," referring to McGregor and his retirement. As part of that speech, a local reporter in Moscow tweeted that Nurmagomedov also compared McGregor and his retirement to "a jealous wife who says I will leave the whole time but then comes back."

And then later that night, McGregor apparently responded by taking a shot at Nurmagomedov's wife instead.

The bad blood between McGregor and Nurmagomedov dates back to last April when McGregor launched an attack on a UFC bus which was transporting Nurmagomedov, several other fighters and employees of the promotion. McGregor was caught on video throwing a metal dolly into the window of a bus at the loading docks at Barclays Center in Brooklyn, New York. Two fighters -- Michael Chiesa and Ray Borg -- suffered minor injuries as a result of the attack. McGregor was later arrested for his actions and pleaded guilty to a misdemeanor disorderly conduct charge. He received no jail time but served community service for his transgressions.

In addition to the sexual assault investigation in Ireland, McGregor is also facing a civil lawsuit in Florida after being charged with stealing the cellphone of someone who was trying to take his photo.