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Azealia Banks' rantings are taking a dangerous turn ... according to her ex-manager who claims she's threatening his loved ones' lives and his.

Jeff Kwatinetz is suing Banks claiming she's inciting her fans to help her with what he claims is a “coordinated campaign of extortion." The ex-manager claims Banks has been harassing him for a while, but recently crossed the line by threatening his family over what she claims are unpaid royalties.

In docs, obtained by TMZ, Jeff says he signed Banks back in October 2014 for her debut album "Broke with Expensive Taste" -- but Jeff dropped her in 2015 for her erratic behavior, and her refusal to promote her album.

Jeff, who runs management agency Prospect Park and co-founded the BIG3 League with Ice Cube -- claims Banks has been ranting on social media since June against him and the agency. He calls her claims the "rantings of a lunatic" ... but adds the rants are getting seriously threatening.

He claims Banks posted YouTube videos and other social media posts in which she threatened his family's lives ... as well as pics of herself outside his L.A. home. He views all the postings as her attempt to incite fans to take up her cause.

In the suit, Jeff says Banks is not owed any dough but believes she will use any means to get what she claims she's owed. He's suing for unspecified damages and wants an order keeping her away from him and his family.