A Southern Cross University campus in the state's north-east is in emergency lockdown and a police operation is under way after an allegedly threatening phone call.

Officers from Richmond Police District and specialist resources were called to the Lismore campus on Tuesday afternoon after the phone call was made to the university.

It is not clear what was said on the phone call or who made it.

Emergency services have received no reports of injuries and there have been no sightings of any potential perpetrators.

Police have advised the public to avoid the area.