Chris Brown & Karrueche

Chris Brown and Rihanna got real -- like REAL real -- by getting cuddly at Jay-Z's concert! Then Chris got REAL by dumping his GF!! Too REAL, right?

Brown announced this morning that he kicked his GF Karrueche Tran to the curb because he wants to concentrate on his "friendship" with Rihanna ... and by "friendship" he means he's going to take her to Bone Town.

Chris Brown's ex-girlfriend ain't buyin' that Chris is "just friends" with Rihanna ... telling her peeps she's convinced they were bangin' behind her back.

We spoke to multiple sources connected to Karrueche Tran ... who tell us KT feels betrayed by Chris because he had promised her that she was the only woman in his life ... especially when she probed him about his feelings toward Rihanna.

We're told Karrueche had suspected something was up between the two of them for weeks because Chris was acting differently -- going to clubs alone, acting distant and ramping up his public appearances with Rihanna.

Sources say Karrueche told friends she truly loved Chris ... and felt that the relationship was great until Rihanna let Brown back into her life.

Chris Brown says he has officially BROKEN UP with his girlfriend Karrueche Tran ... explaining, "I don't want to see her hurt over my friendship with Rihanna."

Brown just made the announcement ... saying, "I have decided to be single to focus on my career. I love Karrueche very much but I don't want to see her hurt over my friendship with Rihanna."

He adds, "I'd rather be single allowing us to both be happy in our lives."

The announcement comes after Brown and Rihanna were spotted together at the Jay Z concert in Brooklyn last night. The two had been hanging around each other A LOT lately ... and did some hardcore flirting at the MTV VMAs.

Karrueche had posted a cryptic tweet last night reading, "Bye baby."

Rihanna and Chris Brown aren't even trying to hide it anymore -- 'cause it looks like they were getting cozy at the Jay-Z concert tonight ... and, based on Twitter, everyone in Brooklyn saw it.

A pic taken from behind RiRi and Chris at Barclays Center is burning up the Internet -- they're seated in VIP ... he's on the left, she's on the right.

No physical contact -- in the photo, anyway -- but Chris' right arm is stretched around the back of Rihanna's chair.

This reunion comes the night after Chris and Rihanna were spotted at the same table in an NYC nightclub.

They were also seen leaving the same hotel on Wednesday -- and, for what it's worth, Chris' blind-as-a-bat GF Karrueche tweeted "Bye baby" ... just a couple hours before tonight's concert.

Apparently, Jay-Z is so powerful he can turn back time ... to 2008.

Chris Brown and Rihanna are barely trying to hide it anymore -- getting up close and personal at a NYC nightclub late Monday night ... then carousing at Rihanna's hotel for hours.

Chris and Rihanna hit up Griffin nightclub in the Meatpacking District -- we're told they arrived 5 minutes apart, and quickly ended up at the same table. Sources inside the club say the two were all over each other, and even disappeared together in a bathroom for 20 minutes.

People inside the club say the duo were kissing and hugging out in the open.

The two left the club separately -- but hours later, Chris was spotted leaving the Gansevoort Hotel, where Rihanna was staying.

By the way, Tuesday afternoon, Chris' clueless GF Karrueche tweeted that Chris sent her roses, a teddy bear and chocolates -- maybe a lame, "I'm sorry."

So we gotta ask ...

Chris Brown’s GF is scared to leave her house without bodyguards by her side -- and she's telling friends, it's all because Rihanna's crazy fans are threatening to kill her.

In case you missed it -- there was a lot of speculation last week that Rihanna dissed Karrueche Tran on Twitter -- posting a pic of a bag of rice cakes wearing sunglasses ... with the caption, "Ima a make u my bitch."

The joke -- Karrueche's Vietnamese ... rice cakes ... etc.

But several of Rihanna's fans took the joke one step too far -- unleashing an avalanche of violent threats on Karrueche ... like "I hope Rihanna beat the dog shit outa yo ass!" ... "Watch yo back" ... and "I will kill you."

Rihanna never admitted the rice cake jab was directed at Karrueche -- but sources close to Karrueche tell TMZ, she now refuses to leave her house without Chris Brown's hired muscle by her side.

As for Karrueche's infamous BF -- we're told CB is 100% supportive of his new lady ... despite getting close with Rihanna recently ... and is urging her not to worry.

Chris Brown and Rihanna are dangerously close to getting back together, sources close to the ex-couple tell TMZ -- but the singers' friends are desperately trying to keep them apart ... for their own good.

According to sources, Rihanna is still head over heels for Chris -- despite that fateful night 3 years ago when he brutalized her -- and if it weren't for the media and her fans, she would already have taken him back.

We're told Chris also has extremely strong feelings for Rihanna -- current girlfriend be damned.

Now, sources tell us, Rihanna and Chris' friends are terrified they'll get back together -- and they're doing everything they can to prevent a possible reunion.

According to sources, friends on BOTH sides have expressed extremely strong reservations to Ri and CB about spending so much time together ... warning it's a terrible idea ... personally AND professionally.

But with Rihanna's birthday ... Chris and Rihanna's duets released this week ... friends fear they're fighting an uphill battle.

As one source put it, "You can't hold back love."

Rihanna and Chris Brown have reconciled ... at least professionally ... because the former couple have collaborated on 2 brand new songs.

It's only been 3 years since Brown pummeled Rihanna's face during a late night argument in L.A. ... but the singer and her ex-con ex-BF have each released songs featuring the other's voice. One is a remix of Rihanna's song, "Birthday Cake" and the other is a new version of Chris Brown's, "Turn Up the Music (below)."

Both songs hit the Internet this week ... and both Rihanna and Brown have been pushing the songs on Twitter.

The songs seem to prove the rumors ... that Rihanna has forgiven Brown and is willing to move on. Earlier this week, Brown tweeted Rihanna "Happy Birthday" ... and Rihanna actually responded, "Thanks."

Rihanna is currently in London (see photo above) ... and Chris Brown was most recently seen in Miami.

Lost in all the Chris Brown/Rihanna possible reunion madness is the fact that CB has a serious girlfriend -- and sources close to her tell TMZ the two of them are doing quite well in their relationship ... thank you very much!

Sources close to Karrueche Tran tell TMZ she is unfazed by the recent rash of RiRi rumors. In fact, we're told CB and KT are now actually living together.

As for CB showing up to Rihanna's birthday party, we're told that didn't bother Karrueche either ... because he came home to her that night and whisked her to Miami the next day to celebrate Valentine's Day.

According to our sources, Chris professes his love to Karrueche daily and he has no plans to leave her for Rihanna.

Chris Brown and Rihanna are NOT back together, despite rampant rumors to the contrary ... Breezy's rep tells TMZ.

As we previously reported, Chris and Rihanna were spotted out at the same West Hollywood nightclub Sunday night. They left separately, but there was lots of speculation that the two had gotten back together.

But that's not true -- according to Chris' rep, the singer was with his actual girlfriend last night ... an aspiring model named Karrueche Tran ... not with Rihanna.