Where in the World is Mount Mantap?

Mount Mantap is in the news:

North Korea has constructed an underground tunnel for possible use in a nuclear weapons test, a Grand National Party lawmaker with close ties to the intelligence community said [September 21, 2006].

Chung Hyung-keun cited sources in the National Intelligence Service for his claim. He said a shaft 700 meters (0.4 miles) deep has been sunk into Mount Mantap in North Hamkyong province with a horizontal tunnel running nearby. (Source)

But where in the world is Mount Mantap? I cannot find it. At best I can limit it to the region shaded in the map. That’s where North Korea has its Musudan-ri missile facility.

While searching, I found this interesting opinion.

[C]arrying out nuclear tests inside North Korea would be an extremely sticky action. That is because this kind of nuclear testing could only be carried out underground. There is absolutely no way they could do in the air or above ground. Even with underground nuclear testing, you normally need a fifty to sixty kilometer square of desert for a nuclear test. In the U.S., this would be something like the Nevada desert. Unless you have the kind they have in India or Pakistan, you cannot do it. The reason for this is that the underground water system gets damaged. North Korea has a very abundant flow of underground water, and if you carry out an underground nuclear test in this kind of place, radioactive materials would get into the water supply for the whole of the Korean peninsula, and also flow out into the Sea of Japan. As a consequence, if there were any underground nuclear testing in the Korean peninsula, it would not be just the ecological system, but also the topography of the land that would be damaged. (Source: 1, 2)

If you know where Mount Mantap is, please tell me.

Update: See Where in the World is Mount Mantap? (Part 2).