Arkansas State University in the US was locked down after armed men were reportedly seen on campus.

The university, based in Jonesboro, sent an emergency alert shortly before 2pm local time on Sunday saying the men were seen near the student union.

A later message said three men wearing all black were seen and that the lockdown remains in effect until further notice.

The lockdown is the second at the school in the last three months ASU.

A man with a shotgun drove onto campus on December 10. That incident ended peacefully as the man eventually surrendered.