WASHINGTON, Aug 9 — A 20-year-old man armed with an assault rifle has been arrested at a Walmart store in the midwestern US state of Missouri and charged with making a "terrorist threat,” police said.

Dmitriy Andreychenko, who was wearing body armour and fatigues, was detained by an armed off-duty firefighter who held him until police arrived, police said.

No shots were fired and no injuries were reported in the incident yesterday in the city of Springfield, which has a population of around 160,000.

Springfield police said Andreychenko has been charged with making a terrorist threat.

"At this time, the investigation is on-going and we are working to determine his motives,” police said in a statement.

The incident came less than a week after an avowed white supremacist killed 22 people in an attack at a Walmart in El Paso, Texas, and another gunman shot dead nine people in Dayton, Ohio. — AFP