Chris Brown has been accused of hitting Rihanna on previous occasions during their "volatile" relationship.

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The 19-year-old singer - who has been charged with making criminal threats following Sunday's (08.02.09) alleged violent attack on the 'Umbrella' star and released on $50,000 bail - reportedly has an aggressive streak which manifested during a previous argument.

Friends of Rihanna claim they saw bruises on her neck last December, adding the pair's relationship was "volatile".

One pal told Us Weekly magazine: "I asked if everything was OK with her and Chris. She told me, 'We broke up again.' I didn't pursue the issue further."

It has also been revealed Rihanna had been working on a song about killing a cheating partner when she was allegedly attacked by Chris.

The 20-year-old pop beauty had teamed up with rapper Akon on the track 'Emergency Room', in which she fantasises about exacting revenge on an unfaithful boyfriend by hospitalising him and then removing his drip.

Rihanna sings: "I'm going to leave your heart broken on the floor/ You're gonna be in the emergency room/ I'm standing by your bed/ And so tempted to pull out your IV.

"Tryin' to call a nurse but nobody can help you now/ Let me see you try to live without me/ Now where's your heartbeat?/ Flatline on the ECG."

The singer has reportedly alleged Chris beat her and choked her until she was unconscious after they began arguing when they left a pre-Grammys party in Los Angeles on Sunday.

It has been claimed the couple began arguing in Chris' silver Lamborghini after he received a text from another woman.

A source said: "He got a booty call. He got a text. Rihanna saw it and she got upset. They started to argue. She got out of the car. He wanted her to get back in, so he grabbed her. She pulled away. That's when she's told people he hit her."

Rihanna's injuries - which police have described as "horrific" - were said to be so bad officers drove her to hospital as soon as they arrived on the scene.

She had bruising to her face, a split lip and bite marks and it has been claimed her eyes her eyes were so swollen she could barely open them for police photographs. The singer may now need cosmetic surgery to correct the damage.

It has also been revealed police have previously been called to a violent scene involving Chris.

In 2007, officers attended his Miami hotel room after he was heard screaming and throwing dishes at his mother.

A source said: "He was fighting with his mom. Neighbouring hotel guests alerted security and they came upstairs to the room, saw the broken dishes and the mess, and then asked his mother to leave the room. Police were then called, but charges were not filed as Chris simply paid the hotel bill and left the hotel."