BRUSSELS (AFP) - Nato Secretary General Jaap de Hoop Scheffer launched Thursday an inquiry into the "unacceptable" leaking of confidential military documents on how to deal with Afghan drugs smugglers. "The secretary general considers it is unacceptable that confidential documents have been leaked," his spokesman, James Appathurai, said. "He is calling for an immediate investigation into the matter, which will be pursued vigorously," he said. "He has not, and never has, issued illegal orders," the NATO statement said. "Our nations' security and the safety of our servicemen and women depend on adherence to NATO security regulations and the protection of classified material," it said. Appathurai declined to confirm the contents of the directive, saying what had been sent to military commanders was "not an order but guidance."