Law enforcement sources tell TMZ ... two men broke into the rapper's Calabasas property Saturday around 8:30 PM PT, apparently having smashed through a rear door to gain entry. We're told Nas's team became aware of their presence due to a Ring camera.

When the two guys were leaving, we're told the crew saw them ... and they called the cops. By the time officers arrived, the two dudes were long gone. Nas wasn't home, BTW -- he was in NYC for an album release party. Nobody else was at the house either, it seems.

As for the damage done ... our sources say the guys tore the place apart and left with at least two bags worth of stuff. Unclear what exactly was taken, or how much it's worth.

We're told Nas is still out of town and will have to come back and do a proper inventory of the items stolen, which will then give authorities an idea of what they're looking for. No arrests have been made and the Los Angeles County Sheriff's Department is investigating.