South Korea's Foreign Ministry said Tuesday the Democratic People's Republic of Korea (DPRK) cannot unilaterally nullify the 1953 armistice that suspended the Korean War.

"The terms of the Armistice Agreement cannot be unilaterally rendered invalid or terminated," Foreign Ministry Spokesman Cho Tai-young told reporters in a briefing. "We demand North Korea ( DPRK) withdraw statements that threaten regional peace and stability."

The remark came after the DPRK declared the truce invalid following a fresh round of U.N. sanctions over its February nuclear test.

The threat also came shortly before South Korea and its ally, the United States, press ahead with their annual joint military drills the DPRK sees as a pretext for invasion.

South Korea will "deal sternly with" attempts to scrap the agreement and "strengthen cooperation" with the United States and China on the issue, Cho said.