"If South Korea does not respond to our ultimatum, our military counteraction will be inevitable and that counteraction will be very strong," North Korean U.N. ambassador An Myong Hun said.
"The situation of the country is now inching closer to the brink of war," Ji Jae Ryong, North Korean ambassador to China, said on Friday.
South Korean Defense Minister Han Min-koo accused North Korea of pushing the situation "to the utmost level."
"North Korea's offensive action is a despicable crime that breaks a ceasefire agreement and the non-aggression treaty between North and South.
"If North Korea continues on provoking, our military -- as we have already warned -- will respond sternly, and end the evil provocations of North Korea," Han Min-koo said.