Section 6. Whenever there is reason to believe that such a nuisance is kept or maintained or exists in any town, either the district attorney for the district, or the attorney general, in the name of the commonwealth, or a citizen in his own name, may bring a civil action perpetually to enjoin the person conducting or maintaining the same, and the owner, lessee or agent of the building or place in or upon which such nuisance exists and their assignees from directly or indirectly maintaining or permitting such nuisance.