Ray J -- Breakup with Girlfriend Triggers MASSIVE Fight Over Miniature Dog

Ray J and girlfriend Princess Love broke up Thursday night and things went nuclear when she tried to leave with their dog Boogotti ... and a huge custody battle for the pup is now underway.

According to our sources, when the "Love & Hip Hop" stars called it quits, Ray offered to leave while she packed her belongings. But we're told when she started to pack up Boogotti's things, Ray J went off.

Our sources say the two went at it over the three-pound Maltese puppy, to the point where Ray J's security had to step in.

We're told Ray J's security guard eventually got hold of Boogotti and the dog is with Ray J now ... but our sources also say Ray J knows this won't be the the end of the battle.

Princess Love took the fight to Instagram and posted an old photo of her with Floyd Mayweather.

Cold blooded.