Grammy-winning musician Lil Nas X pleaded not guilty on Monday to four felony charges after police say he assaulted officers who approached the singer while he was found wandering the streets of Los Angeles in his underwear.

A judge set bail at US$75,000 and said the "Old Town Road" rapper must attend an outpatient drug rehabilitation program. Police said they believed Lil Nas X was using drugs at the time of the incident.

His attorney, Christy O'Connor, however, said there was no evidence of drug use by the 26-year-old.

"This is just an aberrant episode in an otherwise productive life," she said.

The musician was charged with three counts of battery of a police officer and one count of resisting an officer.

He appeared in court in blue prison garb and replied "yes" when asked if he understood the bail conditions.

Lil Nas X, whose real name is Montero Lamar Hill, was the first openly gay man to receive a Country Music Association Award, winning for his 2018 hit "Old Town Road." He also earned two Grammys for the song.

His father, Robert Stafford, told reporters outside the courthouse that the singer was "very remorseful for what happened."

"He's going to get the help that he needs," Stafford said. "Just keep him in your prayers." (Reuters)