Danny Garcia has unified the light-welterweight division after knocking out Amir Khan in four rounds.

Khan made a positive start and used his speed advantage to land a number of solid combinations during the opening two rounds.

However, the Brit then hit the floor for the first time as a light-welterweight late on in round three after Garcia landed a huge left hook to his jaw.

A groggy Khan got to his feet and was allowed to continue after the count had reached eight.

That punch was the beginning of the end though, as Garcia sensed his chance and went after his opponent in round four, knocking him down again with a glancing left hook.

The referee counted Khan to eight again but, despite the 25-year-old's protestations that he was fit to continue, the match was ended.