"Intelligence is collected every day, every hour. It (blasts) is not a failure of intelligence agencies...who ever has perpetrated the attacks has worked in a very clandestine manner," Chidambaram told reporters.
The blasts should not be treated as an attack on India`s commercial capital or markets, he said, adding that the places where the blasts took place were chosen for the high density of population.
"Lets not draw inferences that one community or one religious group are target," Chidambaram said, when asked whether the blasts taking place at Zaveri Bazar and Opera House meant that any specific community was targeted.
About 30 per cent of the diamond market in the area has shifted to the BKC complex in suburban Bandra, he said.
To a query on who was behind the blasts, he said, "We have made it clear to Maharashtra Police not to rule out any angle... We will probe every hostile group. We are not ruling out anything."
Chief Minister Prithviraj Chavan said there was no "credible input" from intelligence agencies on the blasts.
Maharashtra Government would go into issues like modernisation of the police machinery and steps needed to avoid recurrence of such incidents, Home Minister R R Patil said.