Conor McGregor has reacted to Islam Makhachev's win over Alex Volkanovski, insisting that the Dagestani's finishing blows were illegal and could have seen him disqualified.

Makhachev defeated Volkanovski at UFC 294 with a devastating head kick and punches in Round 1 of their lightweight title showdown in Abu Dhabi.

It was an impressive performance from Makhachev and settled whatever debate still remained from the pair's first bout in February.

The lightweight champion started well and out of seemingly nowhere bounced a left high kick off the Australia's head, sending him crashing to the canvas.

Makhachev quickly followed him to the ground, landing short hammer-fists as blood ran down Volkanovski's face.

Referee Marc Goddard realised the fight was over and stopped the bout at 3:06 in the first round.

However, McGregor took to social media after the bout to question the legality of Makhachev's finishing shots - which did appear to strike the back of the Aussie's head.

'A difficult sport to ref,' the Irishman began on X.

'To stop that on a warning or a point deduction when Volk was essentially out already is a tricky one. 

'But there would be grounds for it, 100%. Would have been nail biting stuff. I'd have loved to see it happen. Back of the head shots are not good.'

More than a few fans agreed with the former featherweight and lightweight champ's take on the matter.

'I agree, could see the opinion either way. He was wobbled bad but not impossible to recover if there weren't any back of the head strikes,' replied one X user.

'Exactly what I thought Volk was done but the finishing sequence looks hella dodgy with those back of the head shots,' said another.

'Volk was trying to get up the illegal shots to the back of the head stopped him,' posted a third.

Speaking after the bout, Volkanovski only had praise for his opponent.

'A great set up. A great kick. It's hard, I don't like losing. It hurts me,' Volkanovski said.

'He's a great champion. I back myself every single time and I still stand by that, always back yourself. 

'Islam is one man who you don't want to back yourself [against] if you don't prepare properly because look what he can do to you, he's that good. 

'Credit to him.'