A barrier plug assembly for sealing a subterranean wellbore is located inside a tubing and can comprise a frangible barrier element stacked on a carrier ring, a locking sleeve located above the carrier ring and located in a closed fluid chamber, a valve located on the closed fluid chamber and in pressure communication with the tubing, a retaining device configured for locking the a carrier ring in place, a crushing element located a distance below the frangible barrier element and configured for crushing the frangible barrier element. The valve can be configured for allowing or preventing fluid communication in between the tubing and the fluid chamber.