Narayanan was delivering a talk at the International Institute for Strategic Studies (IISS), wherein he explained a section of the youth were finding the "new version of jihad" as esposed by Islamic State (IS) in Iraq and Syria, its announcement of a Khalifat, the purity of Islam it talks about, "very attractive".
He added: "It has changed the mindset of those inclined."
He estimated at least 100-150 Indians have signed up to fight for IS.
"The figure could be much higher," he concluded. "Many," he said, "were professionals, like engineers, not deprived people."