Kurnaz was later transferred to the US prison camp at Guantanamo in Cuba where he was imprisoned for four-and-a-half years before being released without charge.

Kurnaz alleges that the German soldiers who came to interrogate him in 2002 mishandled him while he was being detained near Kandahar.

Investigators plan to question two new witnesses from Britain who were held alongside Kurnaz in Afghanistan. They will be asked to testify whether a certain type of truck existed in the camp. The incident is alleged to have taken placed behind this vehicle.

Remaining suspicion

"If we did not attach any significance to this, we would not be reopening the investigations," chief prosecutor Walter Vollmer told DPA news agency.

Prosecutors dropped the charges of grievous bodily harm in May because of lack of evidence. A statement issued at the time stated the case was being discontinued "despite remaining doubts about the account given by the accused and despite the fundamental credibility of Murat Kurnaz's account."

A date has not yet been set to hear the witnesses' testimony.

Allegations denied

The two KSK soldiers have rejected the claims, but they have accepted that they did have contact with Kurnaz in the camp in January 2002.

Murat Kurnaz was released from the camp at Guantanamo and returned to his family in Bremen last summer after German Chancellor Angela Merkel intervened on his behalf in Washington.

A German parliamentary panel that was set up to probe whether the German intelligence services had violated human rights in the fight against terrorism is also currently examining the case of the 25-year-old German-born Turk.

The committee is also examining what role the former government played. The former Social Democrat-Green coalition has been accused of aiding the US's illegal rendition operations to kidnap terrorist suspects and then take them to third countries.