The bomb, which was an improvised explosive device (IED), allegedly planted by suspected insurgents with a timer went off yesterday partly damaging some trees but no one was hurt, they said.
The spot where the bomb exploded is just behind the Lamphel police station, they said, adding that an investigation would be conducted how the bomb was planted or hurled in the office complex of the Central intelligence agencies in the high-security area.
The incident occurred barely 12 hours after a powerful grenade, allegedly hurled by the insurgents, was found on Wednesday last inside the heavily-guarded complex of the Manipur secretariat (south block).
Banned Revolutionary People's Front (RPF), political wing of the People's Liberation Army (PLA), in a statement claimed responsibility for the bomb attack at RAW office alleging the office was involved in informing the whereabouts of insurgents, strategy adopted by ultras.
Yesterday's explosion was the fifth of its kind by insurgents this month.