Chart star Rihanna has described the horror she felt as her ex-boyfriend Chris Brown was biting and punching her during a violent argument, saying she saw "no soul in his eyes".

"There was no person when I looked at him," the 21-year-old singer said during an interview on US TV network ABC's primetime news show 20/20 and also on Good Morning America.

"He had no soul in his eyes. Just blank."

Brown was arrested on February 8, hours after he was accused of beating Rihanna after the two argued over another woman. The singer later pleaded guilty to assault.

In the interview, Rihanna, who is no longer with Brown, described him as "definitely my first big love".

"The more in love we became, the more dangerous we became for each other - equally as dangerous," she said. "It was a bit of an obsession almost."

The attack occurred in Los Angeles as Brown drove a rented sports car.

She said it was triggered when she saw a text message on his phone from another woman and confronted him about it.

During the case it emerged Brown hit, choked and bit Rihanna and tried at one point to push her from the car. "It was ugly," she said.

During the beating, the singer said she had no idea how it would end: "That's all I kept thinking the whole time, When is it going to stop? When is it going to stop?"