The tabloid newspaper Bild, which carried the photos, says they show German troops in Afghanistan in 2003.
On one of the pictures, a soldier is seen holding the skull next to his exposed penis, on another – soldiers pose with the skull on their jeep.
“We can’t use such people in our army,” Bernhard Gertz, head of the main organisation representing German troops, said on ARD television channel. “We must investigate exactly how such degeneration and misbehaviour can happen despite good training and good supervision,” he added.
The Bild newspaper did not say how it had obtained the photographs, nor gave any proof of their authenticity.
It is not clear where the skull in the pictures came from, the newspaper admitted, adding that according to a military source it could have been taken from a mass grave.
Germany has about 2,800 troops stationed in Afghanistan within Nato’s International Security Assistance Force (Isaf). Last month, the Bundestag, the lower house of the German parliament, voted to extend the mission of the German forces in Afghanistan until October next year because of the worsening security situation there.