The BBC's Korea correspondent Steve Evans says the South is using the same bloodcurdling rhetoric that the North frequently uses about the South Korean government in Seoul.
He says there has been rising criticism within South Korea of the government as its attempts to isolate the North have failed to deter leader Kim Jong-un's nuclear ambitions.
News of South Korea's attack plan for the North is believed to have been revealed to parliament following Friday's nuclear test.
http://www.bbc.com/news/world-asia-37331852