The Barbados-born singer was pictured bruised and with a split lip after Brown attacked her in his car in 2009.

In a new documentary, he said Rihanna had been kicking and hitting him during an argument about another woman before he "really hit her" and bit her arm.

He said he felt like a "monster" and the fight would "haunt me forever".

Brown received five years probation and a community service order for the assault.

In the documentary, Chris Brown: Welcome to my Life, he said the relationship started going downhill after he admitted being unfaithful with a former employee, despite previously denying it.

After that revelation, Brown said Rihanna "hated" him and their relationship turned increasingly volatile.

"She didn't care, she just didn't trust me after that," he said. "From there, it just went downhill because it would be fights, it would be verbal fights, physical fights as well...

"We were fighting each other. She would hit me, I would hit her. But it never was OK."

'I was in shock'

The infamous 2009 assault happened on the way back from a party where Rihanna spotted the other woman.

She then found a message from her on his phone, which led to them "arguing and arguing and arguing" in the car, he said.

"I remember she was trying to kick me. It was just her just being upset. But then I really hit her. With a closed fist, like I punched her and it busted her lip. And when I saw it I was in shock. Why the hell did I hit her?

"From there, she just spit in my face, spit blood in my face, so it enraged me even more. It was a real fight in a car."

He said he realised it was a "petty, stupid fight" and pulled over, and Rihanna drove home on her own.

Of the police picture of Rihanna that showed her injuries, he said: "I look back at that picture and I'm like, 'That's not me, bro'. I hate it to this day.

"That's going to haunt me forever."