The United States Marine Corps once again did damage control after a photograph surfaced of a sniper team in Afghanistan posing in front of a flag with a logo resembling that of the notorious Nazi SS - a special unit that murdered millions of Jews, gypsies and others.

The Corps said in a statement that using the symbol was not acceptable, but the Marines in the photograph taken in September 2010 will not be disciplined because investigators determined it was a naive mistake.

The Marines believed the SS symbol was meant to represent sniper scouts and never intended to be associated with a racist organization, said Major Gabrielle Chapin, a spokeswoman at Camp Pendleton, California, where the Marines were based.

"I don't believe that the Marines involved would have ever used any type of symbol associated with the Nazi Germany military criminal organization that committed mass atrocities in WWII," Chapin said. "It's not within who we are as Marines."

The Corps has used the incident as a training tool to talk to troops about what symbols are acceptable after it became aware of the photograph last November, Chapin said.

The image has surfaced on an Internet blog, sparking widespread outrage and calls for a full investigation and punishment, including bringing those in the photograph and anyone who condoned it to court-martial.

"This is a complete and total outrage," said Mikey Weinstein of the Military Religious Freedom Foundation, headquartered in Albuquerque, New Mexico. His organization sent a letter to the head of the Marine Corps, General James Amos, and Defense Secretary Leon Panetta on Thursday, demanding punishment for those involved.

It was the second time this year the Marine Corps had to scramble to contain the damage after images were posted on the Internet of troops in inappropriate acts. Last month, Pentagon leaders faced the fallout from an Internet video purporting to show four Marines urinating on Taliban corpses - an act that appears to violate international laws of warfare and further strains US-Afghan relations.

Panetta called Afghan President Hamid Karzai to offer assurances of a full investigation, and the top Marine general promised an internal probe as well as a criminal one.

The Marines in the picture are no longer with the unit. Chapin said she did not know if they are still in the Corps.

In the photo taken in Sangin in Helmand Province, members of the Marine Corps unit are seen posing with guns in front of an American flag and a large, dark blue flag with what appear to be the letters "SS" in the shape of white jagged lightning bolts.

The SS, or Schutzstaffel, was the police and military force of the Nazi Party, distinct from the general army.