South Korea's military will "respond powerfully" to attack or provocation from it's neighbour in the North, the country's president said on Monday.
Park Geun-hye made the statement in response to North Korea declaring a "state of war" between the two countries on Saturday.
Speaking to journalists and military officials he said: "The reason for the military's existence is to protect the country and the people from threats.
"If any provocations happen against our people and our country, it should respond powerfully in the early stages without having any political considerations."
South Korea and the United States have carried out joint military operations in the area.
Last week nuclear ready B-52 bombers conducted dummy run raids in the area in a thinly veiled attempt to demonstrate military might.
North Korea has raised tensions in the region by successfully testing a third nuclear weapon and issuing increasingly bellicose statements to the alarm of western governments.
Saturday's declaration from Pyonyang said: "From this time on, the North-South relations will be entering the state of war and all issues raised between the North and the South will be handled accordingly.
"The long-standing situation of the Korean peninsula being neither at peace nor at war is finally over."
The declaration continued: "If the US and the south Korean puppet group perpetrate a military provocation for igniting a war against the DPRK in any area including the five islands in the West Sea of Korea or in the area along the Military Demarcation Line, it will not be limited to a local war, but develop into an all-out war, a nuclear war."
The statement was accompanied by pictures of North Korean supreme leader, Kim Jong-un, in an "emergency meeting" with top generals.
The US and South Korea has responded with a series of purposefully obvious military operations.
US military command in South Korea said: "[North Korea] will achieve nothing by threats or provocations, which will only further isolate North Korea and undermine international efforts to ensure peace and stability in Northeast Asia," reports Reuters.