Britain's former heavyweight world champion Anthony Joshua demolished former UFC heavyweight champion Francis Ngannou with three knockdowns in two rounds at Riyadh's Kingdom Arena on Saturday.

Joshua sent the 37-year-old Cameroon-born fighter to the canvas in the opening round of their "Knockout Chaos" fight with a straight right to the chin and then felled him twice more in round two.

Ngannou, in only his second professional bout after losing on a split decision to WBC champion Tyson Fury in Riyadh last October, beat the count on the second knockdown but there was no coming back from the third.

Joshua sent him crashing as the referee stepped in and waved the fight off.