Anthony Joshua has produced one of the highlight knockout reels of his career to defeat Francis Ngannou inside two rounds in Saudi Arabia.

With Ngannou, the former UFC heavyweight champion, having dropped Tyson Fury on his professional boxing debut in October, it was felt that there was enough jeopardy in this fight where he could upset the two-time heavyweight boxing champion.

However, as the clock ticked past 3.30am in Riyadh, Joshua made a mockery of some of the pre-fight predictions, ruthlessly sending Ngannou to the canvas on three occasions inside the first six minutes.

Ngannou had initially started the contest looking sharper than he did against Fury, again boxing with poise and searching for an opening as Joshua remained patient.

A surprise switch to southpaw changed everything for Ngannou. Joshua put him down with a huge right hand with the Cameroonian ending the round evidently stunned from being felled so easily.

As round two progressed, the writing felt on the wall, yet few would have foreseen Ngannou being knocked out so devastatingly towards the back end of the round.

To Ngannou's credit, he valiantly beat the count after hitting the canvas from another huge right hand, but he was out cold before he hit the floor with the third - the 37-year-old a sitting duck for Joshua to load up and detonate arguably the biggest knockout of his career.

Joshua showed class and barely celebrated as Ngannou received immediate medical attention, with it taking several minutes before he sat up and eventually got to his feet, but the MMA fighter was later able to share an embrace with Joshua.

With Fury and Oleksandr Usyk putting their world titles on the line in an undisputed fight on May 18, Joshua must now wait to see whether he will fight one of those, or head into a clash with Filip Hrgovic for the soon-to-be-vacant IBF belt in the summer.

On the undercard, Joseph Parker twice got off the floor to edge out Zhilei Zhang by split decision to win the interim WBO heavyweight title.

However, Nick Ball was controversially denied victory in his WBC featherweight title fight against Rey Vargas, the bout ending in a split-draw despite the Liverpudlian appearing to have done enough for the win courtesy of two knockdowns.