A British defense news outlet says that North Korea is building a fortified structure near the port city of Sinpo that will have what appears to be two covered docks that could shelter ballistic missile submarines.

IHS Jane's Defence Weekly reported Friday that the new base, located two-point-two kilometers south of the Sinpo shipyard on the east coast, may be the largest active military building project in North Korea at the moment.

The report said that commercial satellite imagery shows construction of the base began sometime between August 2009 and November 2012. 

Sinpo port is where a North Korean submarine with a displacement of two thousand tons is docked. The North has been test-firing submarine-launched ballistic missiles(SLBM) from this sub in nearby East Sea waters including a launch on July ninth.