Oksana Grigorieva alleges Mel Gibson had thrown TV at his first wife

Mel Gibson's ex-girlfriend Oksana Grigorieva has claimed that Gibson was physically abusive towards his first wife also.

Grigorieva also claims that she has seen the actor hitting his youngest son, Tommy.

Quoting a source "familiar with" the law enforcement investigation into Gibson's behaviour, Grigorieva, 40, claims she saw the actor hit Tommy, his youngest child from his first marriage. The incident purportedly occurred two-and-a-half years ago at a hockey game in Los Angeles, according to RadarOnline.com.

"She [Grigorieva] said that Mel, in her presence, hit Tommy, in the head, while they were in a box watching a hockey game...Tommy started crying and whimpered for the remainder of the game, choosing to sit by himself, away from his father," the New York Post quoted the source as telling the entertainment website.

A Russian newspaper, Komsomolskaya Pravda , reported that Grigorieva had alleged Gibson told her he had thrown a television at his first wife, Robyn Gibson, during a heated argument.

However, Robyn has previously defended her husband of 28 years, following the release of a series of explosive recorded phone calls between the actor and his ex-girlfriend.

The mother of seven of Gibson's children denied the Lethal Weapon star was ever physically abusive during their marriage.

"Mel never engaged in any physical abuse of any kind toward me before, during or after our marriage," she wrote in a statement filed in a California court, TMZ reported.

"Mel was a wonderful and loving father," Robyn added.