Recalling the horrific 9/11 terrorist attack in the US, Prime Minister Narendra Modi said here on Wednesday that terrorism has now become a "global threat" and an "ideology" not confined to any single nation and is deeply rooted and flourishing in Pakistan.

"Now terrorism has become an ideology which is not confined to the boundary of any nation. This is a global problem and has become a global threat whose deep roots are situated in our neighbouring country and are flourishing there," he said at "Swacchata Hi Seva" programme here.