Abstract: A blast mitigation device having a first inner bag intended to house an explosive and further including a second outer bag to freely contain the first bag. Structural connections between the first and second bag are absent. The first and second bags each include a flexible tubular body made of textile material, provided with at least one openable mouth at one end of the flexible tubular body. The mouth is closable by a zip fastener or zipper and wherein at least the second bag includes a closure belt or strap arranged astride the openable mouth, such that in the assembled and use condition the zip fastener or zipper is wound inside a roll of an end portion of the body of the corresponding bag. The roll is kept in position by the at least one strap.