LOS ANGELES — Chris Brown has pleaded not guilty Monday to threatening and assaulting his girlfriend, fellow music superstar Rihanna.

The 19-year-old R&B singer appeared in a Los Angeles courtroom alongside his lawyer, Mark Geragos. Brown entered his plea in a soft voice, while his mother sat in the first row.

He was charged in March by Los Angeles County prosecutors with felony assault likely to cause great bodily injury and making criminal threats. He was arrested nearly a month earlier after police said he was involved in an altercation with a woman who identified the “Run It!” singer as her attacker. If convicted, Brown could face nearly five years in prison. The Associated Press