UPDATED 8.56pm: The New Zealand Islamic Federation isn't surprised by revelations New Zealanders have been talked out of joining Islamic State militants by the SIS.

Prime Minister John Key told media today some people have been "talked down" from linking up with the extremists.

John Key says it's "not unheard of" for families to get in touch with police, and ultimately the SIS, to raise concerns about relatives who may have been radicalised.

"Yeah there are some people that we believe we've actually talked down from wanting to get engaged and leave.

"As I say, the numbers are quite small, but there are cases where family members do become distressed and concerned by the activities they see and they approach, usually in the first instance, the police."

Islamic Federation president Anwar Ghani says his organisation made authorities aware of some of the individuals.

"I wasn't surprised. I've been aware of one or two characters and that was communicated to police."