Five Tunisians, a Turk, an Egyptian, a Moroccan and a Pakistani were expelled, Alfano told a press conference, adding that he was "sure other expulsion orders will follow".
He also said more than 100 people were being closely watched on suspicion of sympathising with or plotting to commit "jihadist, terrorist activities".
"We are faced with an imminent threat which could be carried out in any part of our continent. Faced with this potential danger we have raised security to the highest level," he said.
"Ours in a job which must necessarily be carried out in the shadows, but believe me it is carried out without stop, against terrorism, to defend our democracy and freedom."