Police are investigating an alleged armed robbery in the Bankstown area overnight.

Just before 7pm (Sunday 4 September 2016), police were called a store on Cooper Road, Yagoona, following reports of a robbery.

Police have been told, prior to their arrival, a witness saw four men enter the store. He has then locked the external entry door to the store, locking the men inside.

Police from Bankstown Local Area Command attended and allegedly found four males trapped inside the premises, ransacking the store and assaulting a 51-year-old male attendant.

When officers arrived they allegedly forced entry into the store and arrested four men at the scene.

There was a significant amount of damage made to the store during the incident.

The men have been taken to Bankstown Police Station and are currently assisting with inquiries.

NSW Ambulance Paramedics attended the scene and treated the 51-year-old man for his injuries. He was taken to hospital in a stable condition.