The altercation apparently happened because Clooney thought one of Fabio's five female dinner guests was photographing him.

But a source told "Access Hollywood" Fabio approached Clooney's table to explain he was having a charity dinner for the California Highway Patrol's 11-99 Foundation and his guests were only taking photos of each other -- not Clooney.

However, a photo obtained by the news magazine indicates one of Fabio's guests did take a picture of Clooney flipping them the bird.

The source said Clooney and Fabio traded barbs, then had to be physically separated.

"The women and I were taking pictures of us together only," Fabio told "Access Hollywood." "The women were not taking pictures of George. Out of courtesy, I even went over to George's table to explain that to him. I just feel badly that it ruined the night of these women who paid to support charity. I am thinking of something to make it up to them."

Fabio's manager, Eric Ashenberg, said, "Clooney started on 'ER' and Fabio was going to send him back there."