TMZ has confirmed ... Mel Gibson is caught on tape, screaming at his baby mama Oksana Grigorieva, "You look like a f*king pig in heat and if you get raped by a pack of ni**ers it will be your fault."

The tapes were secretly recorded by Oksana in the midst of their nuclear breakup and custody battle.

We've also confirmed Mel is heard on tape calling Oksana a "whore" and a "c**t."

The tapes have been submitted to the judge in their custody battle and are under seal. Sources say the tapes were recorded prior to May, when Mel and Oksana reached a custody agreement with a mediator.

And TMZ has learned ... Mel sent Oksana a number of incendiary emails that she kept.

TMZ broke the story in 2006 when Mel went nuts on a cop after being busted for DUI, saying, "F**king Jews ... The Jews are responsible for all the wars in the world."