A man volunteering to guard a self-proclaimed "Muslim Free" gun shop in a rural Oklahoma town accidentally shot himself in the arm after dropping his gun, local authorities said.

The Save Yourself Survival and Tactical Gear shop in Oktaha, about 193 km east of Oklahoma City, has a window sign that reads: "This privately owned business is a Muslim Free establishment."

The man involved in the incident has not been identified and his injuries are not life-threatening, Muskogee County sheriff Charles Pearson said.

Islamic civil rights group The Council on American-Islamic Relations filed a complaint with the US Department of Justice, asking for a federal investigation into the establishment.

Armed citizens standing guard at the shop have said the business had received death threats from around the world.

Save Yourself Survival and Tactical Gear said in a posting on its Facebook page the man who shot himself had a broken holster.

"He came over today to help fix a door in my office and as he bent over his weapon fell from a malfunctioning chest holster and went off when it hit the floor," a store manager said.

Reuters