South Korean President Park Geun-hye on Friday warned the North to end provocative actions and wake from the illusion that it will benefit from nuclear armament.
"Reckless provocation will be the road to destruction for the North's regime," Park said at an anniversary event to remember the victims of the sinking of a naval ship in 2010 that killed 46.
South Korea accuses the North of having launched a torpedo to sink the ship which the North has always denied.
"I hope you can maintain maximum combat power and mental strength so that North Korea cannot even dare to launch a provocation," Park added, addressing her country's military.
North Korea's leader Kim Jong Un guided what state media described on Friday as the largest ever exercise of long-range artillery training to blow up the South Korean presidential and government offices.
Kim ordered his military to be on high alert "so that it may mercilessly pound the reactionary ruling machines in Seoul, the cesspool of evils, and advance to accomplish the historic cause of national reunification, once it receives an order for attack," official KCNA news agency said.