Conor McGregor has apparently accused Kamaru Usman of taking steroids as the Irishman upped the ante in his war of words with the UFC welterweight champion after the Nigerian responded to copying accusations.

Usman, 33, has vowed to lap his competition at 170 pounds and got off to a devastating start after knocking out rival Jorge Masvidal in front of 15,000 fans at UFC 261 in Jacksonville, Florida.

The Nigerian Nightmare is expected to take on No 1 contender Colby Covington next, although McGregor has thrown his hat in the ring for a title fight having accused Usman of 'copying' him.

McGregor, 32, took exception to Usman saying it was 'green panty night' when opponents fought him, and accused the welterweight king of copying his fighting style following the sensational one-punch knockout.

'Except when I touch you at 170, they go out,' Usman said, responding to McGregor's copying accusation. 'They don’t even go out at 155 anymore for you. I finish people. You get finished.'

However, The Notorious has hit back, insinuating that Usman's bout with Gilbert Burns was rescheduled due to an undisclosed anti-doping issue.

'Relax there, carbuncles. You big spotty back pox. You were ringside last time I fought at 170. 40 seconds is all it took,' he tweeted. 

'Why did you reschedule Burns fight ? What was the reason, that was never given to the public, why that already signed fight was then rescheduled? 

'Never in all my time in this business, which is long before all of these f*****g bums, have I ever seen a signed fight get rescheduled with no reason given whatsoever. So said fighter can recover from “undisclosed injuries”. Excuse me what? The fight is signed/sealed/tix sold.'

According to HealthLine.com, acne is a common side effect of steroid use. McGregor then said he will end Usman's 14-fight winning streak in the UFC and add a third world title to his collection with his 'two lump hammers'.

'F*** these juice heads anyway, I don’t give a b****x. I’m just calling it as it is. I’ve the biggest balls in Ireland with two lump hammers attached to me elbows. Send me in and I’ll pop that big pimple. Get 3 belts to go with my 3 commas.

'It’s time to really start caving heads in properly with these hammers of mine.' 

Usman responded to McGregor's 'carbuncles' tweet, telling McGregor to 'stay humble'. 

'I offered you the fight and you went missing. Let’s stay humble young man. I already took your pride. Don’t make me take your whiskey too,' he said. 

McGregor has teased a title tilt at welterweight, having fought Nate Diaz and Donald Cerrone at 170 pounds. The Irishman defeated Cerrone in just 40 seconds when they met in January 2020.

For now, the 32-year-old has his sights set on a trilogy bout with Dustin Poirier, having suffered defeat to The Diamond on Fight Island in January. 

McGregor has lost two of his last three fights in the UFC and is bidding to return to the summit of the lightweight division following the retirement of the all-conquering Khabib Nurmagomedov.