South Korean President Park Geun-hye said on Monday there will be a strong and swift military response to any further North Korean provocation without regard to political consequences.
This comes after Pyongyang said it was entering a “state of war” with the South two days earlier.
It is angered by new UN sanctions which followed its February nuclear test, as well as the annual joint US-South Korea military drills which are currently under-way.
The US has now sent F-22 stealth fighter jets to to bolster the military exercises.
North Korea also threatened to close down the Kaesong Industrial Park, which serves as the last example of inter-Korean cooperation.
Kim Duk-soo, a South Korean who works in Kaersong, said:
“I’m quite worried but what can I do? I have to go there to work. I don’t know what they’re thinking in the North but how could they close it? They need to make money and the industrial park is their cash cow.”
His compatriot Cho Young-man added:
“Even if the complex gets closed down I hope our workers will be able to come back without being detained.”
Despite the increasingly aggressive posturing it is thought the complex will remain open as it serves as an important source of hard cash for the impoverished North.