A police chief assisting with crowd control during a university protest told his officers to stand aside as protesters tore down a century-old Confederate monument, according to documents.

Messages obtained by the WRAL-TV station show Chapel Hill Police Chief Chris Blue closely monitored the August 20 protest as his officers backed up University of North Carolina police, who take the lead in policing the Chapel Hill campus.

The station used a public records request to obtain about 400 pages of emails and texts to and from Mr Blue on the day of the protest and the day after.

During the protest in a main campus quad, around the statue known as Silent Sam, Mr Blue instructed officers "let's give them lots of space" and "stay way out", the messages show.

At one point he sent a message saying Chapel Hill officers were "too close". Shortly afterwards protesters pulled down the statue.

UNC campus police also took a non-confrontational approach. UNC officers have primary responsibility for patrolling campus, but the two departments assist each other.

The protest had started at a plaza in Chapel Hill before several hundred demonstrators marched across the street to campus.

The actions by UNC campus police are also under scrutiny from university and legislative leaders.

No injuries were reported during the protest. Three people face misdemeanour charges of rioting and defacing a public monument.

Mr Blue received several emails after the protest criticising how his officers handled the incident. He emailed his officers on August 21 and thanked them for their efforts.

Silent Sam was a bronze statue of a Confederate soldier, by sculptor John A Wilson, which had stood in the town since 1913.