There was a Google translation published yesterday (by you?) and there it says that those are mini subs, they cannot stay submerged for long. This means they are only usable for a short mission, probably to deliver divers or mines. SK and Japan may be within range, but they can't cross the ocean. Those subs will become visible very soon (or never.)
It wasn’t by me. But though they are small submarines they are what people generally think of as ‘midget subs’, The two ‘torpedo’ subs are small 130-ton, 30-meter, 10-man machines that can stay submerged for three-to-four days.
http://www.zerohedge.com/news/2013-04-03/two-north-korean-submarines-disappeared
By the way it is one of these small subs that is suspected to have sunk a South Korean ship, the 1,200-ton corvette Cheonan in 2010.