The prosecution has opened an investigation into the alleged maneuvering of labor union activities by the spy agency under the former Lee Myung-bak administration.

On Tuesday, the Seoul Central District Prosecutors' Office raided the Ministry of Employment and Labor to secure documents and hard disk drives related to activities of the country's two largest umbrella labor groups.

Prosecutors said the raid was to verify suspicions that the National Intelligence Service(NIS) carried out maneuvers in 2011 to obstruct activities by the Korean Confederation of Trade Unions and the Federation of Korean Trade Unions.

In an attempt to topple the two labor groups, the spy agency allegedly supported the establishment of a new umbrella labor group.