The bomb was so powerful that the sound of the explosion could be heard from a distance of three km, sources said adding that security and army personnel cordoned off the complex before checking some passers-by.
A team of newspersons who wanted to make an on the spot enquiry was not allowed to enter the M-Sector complex saying they would be allowed later.
Official sources refused to divulge any information when asked whether the bomb was hurled at the four-cornered wall complex by insurgents from roadside or an accidental explosion of grenade or bomb kept inside the army complex.
Manipur fire service office is on the western side of the M-Sector while national highway 39 is in front of it in eastern side. Raj Bhavan adjoining it is in the south while Johnstone Higher Secondary School is in the north.