"Investigation indicated that many of them were previously apprehended for drug use," Nayef was quoted as saying Wednesday by the Saudi Press Agency, SPA.
Saudi authorities killed 15 gunmen and captured several others in confrontations in the northern city of Ras earlier this month.
A Jordanian doctor earlier said a number of the terrorists believed to belong to the Saudi branch of al-Qaida network, were treated for drug addiction in a private clinic in Amman.
He said at least seven of them were treated for advanced addictions to morphine and cocaine.
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