The pop poster girl Rihanna suffered a split lip, bloody nose and scratching to her face after an alleged assault by her boyfriend Chris Brown, it has emerged.

The 20-year-old R&B singer was taken to hospital with contusions and facial swelling, according to several reports today.

Rihanna, who scored a world-wide hit with the song Umbrella, today cancelled a performance in Malaysia planned for Friday. Organisers of the Kuala Lumpur concert said that the show would be rescheduled “in light of recent events involving Rihanna”.

Brown, 19, has been charged with making a criminal threat and remains under investigation on domestic violence allegations. The singer, who was arrested and bailed in Los Angeles on Sunday evening, has pulled out of Sunday’s NBA All-Star basketball game.

Brown, who rose to fame on the back of hit single Run It!, has also had an advertisement he made for Wrigley dropped from American television.

The chewing gum company pulled the campaign yesterday, explaining: “Wrigley is concerned by the serious allegations made against Chris Brown. "We believe Mr Brown should be afforded the same due process as any citizen.

"However, we have made the decision to suspend the current advertising featuring Brown and any related marketing communications until the matter is resolved."

Rihanna and Brown were last seen together in public on Saturday night, when they were photographed happily sitting together at a pre-Grammy party at the Beverly Hilton hosted by the music mogul Clive Davis.

Shortly afterwards, Los Angeles police were called after a witness reportedly heard a woman screaming on the street in the upmarket LA suburb Hancock Park.

In a statement, the LAPD said that Brown and a woman, who they have refused to name as Rihanna for confidentiality reasons, had started arguing in his rented Lamborghini.

Brown pulled over, the pair got out, and the argument escalated into an "alleged domestic violence felony battery".

"The woman suffered visible injuries and identified Brown as her attacker," the statement said.

By the time police arrived, Brown had left the scene.

On Sunday evening, he handed himself in at a police station, and was charged with making a criminal threat and released on $50,000 (£34,000) bail.

Both Brown and Rihanna were nominated for Grammy Awards and were due to perform at Sunday night’s ceremony, but both pulled out at the last minute.

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