Billy Joe Saunders' son punches opponent Willie Monroe Jr at weigh-in

The weigh-in for Billy Joe Saunders' title bout with Willie Monroe Jr was overshadowed when Saunders' son punched the American on stage.

As the pair squared up before Saturday's WBO middleweight title fight, the Briton's son Stevie, reported to be seven, stepped between them.

Promoter Frank Warren put his hands on Stevie's shoulders and Monroe ruffled his hair, prompting the boy to hit Monroe and aim a kick at him.

Saunders defended his son's antics.

The 28-year-old tweeted: "My son's been taught when a stranger puts their hands on them (to) punch and run away (in) self defence."

But Monroe was not pleased, inferring the incident was stage managed and said: "Warren should be ashamed of himself."

Both fighters weighed in at 11st 6lb on Friday.

Saunders has not defended his WBO middleweight title since December and hopes a win at the Copper Box Arena will set up a fight with Gennady Golovkin or Saul 'Canelo' Alvarez.

Saunders has won all of his 24 fights while Monroe Jr has lost twice in 23 bouts.