While the media portrays them as victims, it would be kind of naive to believe it is completely true.
A true "spy", however, is somebody who infiltrates and pretends to be somebody they are not in order to gather information to be kept secret by an opposing entity. If these journalists were going to publish, or had a history of publishing, and were acting as journalists normally do, then for all intents and purposes it makes no difference if they were also acting for an intelligence service or not -- they were journalists.
Countries that don't have freedom of the press can certainly view things differently, but then again, for them all journalists are spies simply by their job description of finding stuff out that used to be private and publishing it. So while NK may have a point, and may even be partially factually correct (I don't know) it's extremely likely that they're also just kidnapping easy targets and using them as pawns.