Watch: The knockout too violent for the UFC

The knockout kick to the head. Photo / Youtube

Any fight that ends in a six second knockout is certain to be brutal, but this was more extreme than most.

Russia's Timofey Nastyukhin fought Australia's Rob Lisita in a featherweight bout at ONE Championship 43 in Thailand on Friday night and it was a one-sided contest to say the least.

A brutal right-left combination from Nastyukhin floored Lisita before the Russian finished his opponent off in the most punishing fashion.

He walked around to the side and unleashed a brutal soccer kick at the Aussie's head, connecting with some serious force before the referee ran in to push Nastyukhin away and end the fight.

Those types of kicks - landed when one fighter is on the floor - are illegal in the UFC and many other promotions because they're considered too dangerous, but are still allowed in some leagues.

Lisita's arms came up involuntarily after copping the blow - a response to being concussed - and a medical professional rushed into the Octagon.

Mookie Alexander of MMA website Bloody Elbow described the KO as an act of "pure violence".

According to Alexander, Nastyukhin has used a soccer kick as the finishing move in each of his victories in the ONE Championship. The win was the fifth time he's ended a fight in less than a minute while it was his third first-round knockout.

His record now stands at 10-2, while Lisita's has moved to 14-8.

The ONE Championship is Asia's largest MMA organisation and hosts fights throughout the region.