Terence Crawford undisputed champion after TKO victory over Errol Spence Jr

Terence Crawford, left, and Errol Spence Jr during their undisputed welterweight championship boxing match (John Locher/ AP)

Terence Crawford has become the undisputed welterweight champion after a dominant performance against Errol Spence Jr in Las Vegas.

Crawford unleashed a flurry of punches in round nine to a wobbly Spence who could not defend himself, forcing the referee to step in and stop the fight.