"The fight was animated, but the incident is over. The two players cleared up their disagreement," Milan chief executive Adriano Galliani was quoted as saying on the italian club's website.
"I'm happy when I see players pumped up, I'm happier seeing fiery training sessions than boring ones."
Reports said Sweden's occasionally combustible Ibrahimovic, an August signing from Barcelona, rashly tackled United States defender Onyewu from behind.
The American, who missed a year of action with a knee injury and has not featured for Milan this term, reacted angrily and the duo grappled before being pulled apart.
‘We were in Amsterdam, so I faked a toothache to go and see Crystal Palace in the FA Cup final. I couldn’t make the replay, though – the Stones worked it out’: Rolling Stones guitarist Bill Wyman feigned injury to watch 3-3 draw with Manchester United
‘Home truths needed to be spoken at Manchester United and Ruben Amorim has been brave enough to do that – the way he’s dealt with Marcus Rashford has been correct’ Former Red Devils star praises new boss
