AYER -- Ayer police are seeking the community's assistance in the hunt for a robbery suspect who struck a Littleton Road gas station.

At approximately 7:47 p.m. Sunday night, a masked man entered Partridge Automotive at 42 Littleton Road. The man demanded cash while brandishing a 6- to 8-inch knife. The clerk was not injured in the incident, and the man was believed to have fled the store on foot. There was no known direction of travel for the suspect.

Rather than estimate what the man looked like or was wearing, the Ayer police request that people review this photo of the man. The image was gleaned from the store's security camera.

Ayer police called in assistance from Harvard, Shirley, Groton, Littleton and state police, which responded with a K-9 unit for a sweep of the area Sunday night. The robbery occurred shortly before the gas station was due to close at 8 p.m., confirmed Ayer Police Lt. Brian Gill. Police are not disclosing the amount of money taken in the robbery, stating the sum itself is important to the investigation.

If you can identify the person in this photograph, or were in the area and observed anything, contact Ayer Police Detective Andrew Kularski or Officer George Fichter at 978-772-8200.