BERLIN - The head of the German armed forces Wolfgang Schneiderhan has resigned over reports the military withheld information about a September 4 air strike in Afghanistan believed to have killed dozens of civilians.

The strike, ordered by a German commander and carried out by a U.S. F-15 fighter, was the most deadly operation involving German troops since World War Two, killing 69 Taliban fighters and 30 civilians, according to the Afghan government.

In the days after the strike, Franz Josef Jung, who was defense minister at the time and now serves as labor minister in Chancellor Angela Merkel's new center-right government, denied there were any civilian victims.

Germany's Bild newspaper reported on Thursday, ahead of a parliamentary debate on extending Germany's 4,500-strong mission in Afghanistan, that videos and a secret military report had clearly pointed to civilian casualties at the time the government and military was denying them.

Speaking in parliament on Thursday, new Defense Minister Karl-Theodor zu Guttenberg acknowledged the existence of the secret report and said he had been unaware of it until Wednesday.

RESPONSIBILITY

This report and others from the previous legislative period were not presented and responsibility for this has been taken at a senior level, Guttenberg said. The inspector general ... has asked me to relieve him of his responsibilities.

The opposition Social Democrats, who were part of the government when the strike took place, called for a parliamentary investigation into the matter.

Jung, a member of Merkel's Christian Democrats, spoke briefly in parliament and asked for time to review the documents in question. He promised to speak to the Bundestag on the matter later in the day.

If it became clear he was aware of the secret reports, he would almost certainly be forced to resign.

Schneiderhan holds the highest-ranking military post in the armed forces and the revelation that details of the strike were withheld are an embarrassment for Merkel's government as it considers increasing the number of German troops in Afghanistan.

The mission has become increasingly unpopular in Germany and other western countries as violence has surged to its deadliest levels since the Taliban was forced from power in 2001.

The air strike was called in by German troops stationed near Kunduz in northern Afghanistan in what they said was a pre-emptive measure to prevent a possible suicide attack by Taliban fighters who had hijacked two fuel trucks.

Afghan President Hamid Karzai called the raid a major error of judgment and it was also criticized by the French and British foreign ministers.

The strike came as a shock to the public in Germany, where opposition to military conflict runs deep more than 60 years after the defeat of the Nazis.

(Writing by Noah Barkin; editing by Andrew Roche)