RiRi and Ci got into a diva catfight!
Rihanna and Ciara -- who both dated Chris Brown back in the day -- bared their claws in a caustic, public spat on Friday.
The trouble began when Ciara, 25, made a dig at the fellow singer on E!'s Fashion Police.
"I ran into her recently at a party. She wasn't the nicest," Ciara sniped on TV. "It's crazy, because I've always loved and respected what she's done in fashion. It wasn't the most pleasant run-in."
(Fashion Police host Joan Rivers put it more bluntly: "B**ch!")
Rihanna, 22, apparently got wind of her rival's remarks. She Tweeted, "My bad Ci, did I forget to tip you? How rude of me....You gangsta huh? Ha."
Retorted Ciara on Twitter: "Trust me Rihanna you don't want to see me on or off the stage."
The "Only Girl" singer's sharp comeback: "Good luck with bookin that stage you speak of."
"Pure comedy," Ciara replied.
Before things got uglier, Rihanna called a truce. "Ciara baby, I love you girl!" she Tweeted. "You hurt my feelings real bad on TV! I'm heartbroken! That's why I retaliated this way! So sorry! Let's make up."
Her pal replied in kind. "Rhi, u know its always been love since day 1! Doing shows and everything. You threw me off in that party! Apology accepted. Let's chat in person."