Murat Kurnaz, a Turkish-born German resident, claimed that two German soldiers of the elite military unit KSK interrogated him in a secret U.S. prison camp in Kandahar, Afghanistan, in January 2002.
One KSK soldier pulled his hair and smashed his head against the ground, Kurnaz said.
Kurnaz identified a soldier after the state prosecution office in Tuebingen, southwestern Germany, showed him nearly 50 photographs of various German troops.
Prosecutors said they were investigating the soldier, as well as his partner, on charges of aggravated assault. "Both suspects are accused of aggravated assault while on duty," the prosecutors said in a statement.
The case is an embarrassment for the German military. Defense Ministry officials first denied that the KSK was in Afghanistan at the time; after questioning soldiers, they admitted to the KSK's presence in Kandahar and to contacts with Kurnaz, but strongly denied that German soldiers had abused him.
The case is part of a parliamentary inquiry that probes Germany's involvement in the war on terror. Reports surfaced that Germany made use of the U.S. extraordinary rendition program by interrogating terror suspects in secret prisons in third countries. Kurnaz, a Turkish national who was born and raised in the northern German city of Bremen, spent over four and a half years in the U.S.-run military prison in Guantanamo Bay, Cuba, before he was released last summer.
German and U.S. intelligence agencies had deemed him not a security risk.