Arkansas State University is on lockdown as reports say that police have surrounded a man with a gun.

He was later said to be in custody.

The school made the announcement via its Twitter feed on Thursday, adding there were no reports of injuries.

"The individual with a weapon has been surrounded by police. No shots have been fired, no reported injuries," it said.

Everyone at the school was told to lock doors and shelter in place.

An Arkansas State spokesman said one person with a weapon was surrounded by police, reported WDRB.

University spokesman Bill Smith says the school was placed on lockdown after the man drove onto campus with a gun.

He crashed his vehicle into a barrier. A green pickup truck parked on grass is believed to be related to the school lockdown.

According to local media in Jonesboro, the entire campus was being shut down as of 2.30pm Thursday afternoon.

The suspect was last spotted outside the school's student union.

A text message to students urged everyone to evacuate.

The university is located about 200km north-east of Little Rock.