Gennady Golovkin shows his belts.

Middleweight marauder Gennady Golovkin retained his WBC and IBF titles when challenger Kell Brook was pulled out by his corner five rounds into a compelling fight in London, late Saturday.

Kazakh Golovkin had won his previous 22 fights by knockout but was rocked by unbeaten welterweight world champion Brook in the early exchanges before his superior power told.

Brook, who suffered a suspected fractured eye socket, won the second round with a left uppercut that produced huge roars from the huge O2 Arena crowd, who were mainly supporting the British underdog.

He was still standing his ground in the fourth but by the fifth it became clear the step up from welterweight to fight the man who has brutally dominated the middleweight division for six years was a step too far.

There was little coming back as Golovkin landed some thumping blows and trainer Dominic Ingle threw in the towel which was initially unseen by the referee.

Some of the crowd booed, but afterwards Brook said the eye injury had left him with restricted vision.

Unbeaten Golovkin took his record to 36 wins.