The US marine corps has confirmed that a sniper team in Afghanistan posed for a photograph in front of a flag with a logo resembling that of the notorious Nazi SS.

Use of the SS symbol is not acceptable, and the marine corps has addressed the issue, Lt Col Stewart Upton said in a statement. He did not specify what action was taken.

Upton said the marines in the photograph, posted on a blog, are no longer with the unit. The picture was taken in September 2010 in Sangin province, Afghanistan.

The photo shows a flag with what appear to be the letters “SS” in the shape of jagged lightning bolts. The symbol resembles that used by SS units in World War II.

The SS, or Schutzstaffel, was the police and military force of the Nazi Party, which was distinct from the general army. Members pledged an oath of loyalty to Adolf Hitler. SS units were held responsible for many war crimes and played an integral role in the extermination of millions of Jews along with Gypsies [Roma and Sinti] and other groups of people classed by the Nazis as undesirables. The SS was declared to be a criminal organisation at the Nuremberg war crime trials.

The Military Religious Freedom Foundation in Washington said it was outraged and wants a full investigation.

Mikey Weinstein with the foundation said he has been flooded with calls from former marines offended by the photo and from one member of his organisation who is an Auschwitz survivor.

“This needs to be fully investigated. This is a complete and total outrage,” he said.

Weinstein said his organisation was sending a letter to the head of the Marine Corps and defence secretary Leon Panetta.

Master Gunnery Sgt Mark Oliva, a spokesman at Camp Pendleton, California, said the photo was brought to the attention of the 1 Marine Expeditionary Force inspector general in November, and he found there was no intent on the part of the Marines to identify themselves with a racist organisation.

Oliva said the investigation found that the SS symbol was meant to identify the marines as scout snipers, not Nazis, but it was nonetheless not acceptable.

This is the second time this year the marine corps has had to do damage control for its troops’ actions.

The marine corps is also investigating a separate group of marines recorded on video urinating on the dead bodies of Taliban fighters.

• This article was amended on 3 August 2018 to capitalise the word Gypsies in line with Guardian style and add the central European designations of Roma and Sinti.