Ajayi had, at various times, served as State Director of the DSS in Bauchi, Enugu, Bayelsa, Rivers, and Kogi States.
The new appointments followed the resignation of the previous NIA and DSS chiefs.
Ngelale said: “President Tinubu expects that the new security chiefs will work assiduously to reposition the two intelligence agencies for better results and charges them to bring their experience to bear in tackling the security challenges bedeviling the country through enhanced collaboration with sister agencies and in surgical alignment with the Office of the National Security Adviser.
“The President thanks the outgoing Directors-General of the two pivotal intelligence agencies for their services to the nation while wishing them success in their future endeavours.”