The nation, which had the information, did not see it as important enough to pass on it on to Indian intelligence agencies until it recognised its significance after the blasts had occurred.
The August 25 twin blasts in Hyderabad killed 42 people and seriously wounded scores of others.
The national security adviser would not identify the country in question.
"Unless countries across the globe join forces and pass on information -- not necessarily linked to a particular incident or to a particular country -- you can't deal with terrorism," Narayanan said.
"Terrorism is no longer a conspiracy hatched in Hyderabad or in Pune or in Chennai or in Delhi. It is much wider," he said. "You need to piece the information sometimes from across the globe. Because planning takes place in one place, logistics in a second place, funding is done in a third country, recruitment in a fourth country and finally, the act is carried out here."
Hyderabad has become vulnerable to terrorism because it is on the radar of the three or four terror networks that are operational in the country, Narayanan said.
"Hyderabad and to some extent Bangalore, Mumbai, Delhi are the four cities where a concentration of terrorist activity has been identified," the national security adviser added.
The Shahid Bilal network is in operation both in Hyderabad and Bangalore, Narayanan said, adding that the terrorists have three or four prongs -- Hyderabad and Bangalore at one level; Varanasi and eastern Uttar Pradesh at another; Maharashtra and Gujarat at a third.
Read National Security Adviser M K Narayanan's exclusive interview with rediff.com
