TODAY | April 03, 2013
>> and defiant act from north korea over the night. workers from south korea now being turned away from an industrial complex that is just over the border.
>> just to give you perspective, the facility is seen as the only real symbol of cooperation between the two countries. leaders in the south have been very quick to respond this morning demanding that their workers be allowed in.
>> let's get to nbc's chief foreign correspondent richard engel , he's in seoul this morning for us. richard good morning, give us the latest on this.
>> reporter: good morning, savannah. the kaesong industrial relationship between north korea and south korea an closing it is seen here as an ominous sign. south korean troops were on the move this morning along the fenced border with the north after pyongyang shut the kaesong industrial park where some 120 south korean businesses operated inside north korean territory. the economic zone was supposed to benefit both sides. cheap labor for south korea , jobs for the north, 50,000 north koreans depend on it. it's a critical source of income for the at times famine stricken pa ryia state but what appears to be economic suicide for north korea is yet another sign of how far it's willing to go, after threatening nuclear war and promising to reopen a nuclear reactor to make more bombs.
>> the united states will defend our allies, and we will not be subject to irrational or reckless provocation.
>> reporter: along the border, south korean soldiers watch for any provocation in this decade's long conflict that neither side has forgotten.
>> north korea dubbed this tunnel in secret in the 1970s for a sneak attack on south korea . it was discovered and now part of the demilitarized zone between the two countries. south korea keeps it open as a remind der of the threat it has long faced from the north. the tunnel was wide enough for 30,000 invading troops to pass in an hour. north korea never got its men through here to conquer the south but it's showing it hasn't given up on this war.
>> and richard, this is a young, untested leader and already seems to be pushing things even farther than his father did.
>> reporter: they both seem to be rational in that they both follow a consistent ideology that sees the north koreans as surrounded, that they have to be strong in order to survive but he certainly does seem more reckless than his father. look at what he's said over the last few days and look at what he has done right now putting 50,000 of his own people out of work, the center of a city of 200,000 that now has no economic base , it is a very big move some people saying he is cutting off his own nose despite his face.
>> richard engel in seoul for us this morning thank you.