The warning came after South Korean President Lee Myung-bak met with his security ministers amid threats of a nuclear test the North has been issuing since last week when the 15-member U.N. Security Council unanimously approved a resolution widening its existing sanctions. The resolution was in response to the North's December long-range rocket launch in violation of U.N. sanctions imposed after its two nuclear tests in 2006 and 2009.
"If North Korea misjudges the situation and pushes ahead with a provocation again, it will cause very grave consequences," Park Jeong-ha, spokesman for President Lee, said, Yonhap News reported.
"The government urges North Korea to immediately halt all provocative words and actions and comply with international obligations." The spokesman, however, did not expand on the "grave consequences" warning.
The spokesman said Lee told South Korea Defense Minister Kim Kwan-jin to maintain strong military readiness, saying North Korea is "escalating military tensions on the Korean Peninsula while overtly threatening additional provocations, including a nuclear test," Yonhap reported.
Yonhap quoted a senior presidential official the North would be making a "big mistake" if it goes ahead with a nuclear test.
"It will be unfortunate for North Korea's future," said the official, who spoke on condition of anonymity. "This is the message we are sending to North Korea." He declined to discuss if South Korea also is considering military options.
South Korea already is in talks with other partner nations regarding punitive steps against the North in addition to those proposed by the United Nations. Earlier, South Korean experts said the North has completed all preparations for testing its third nuclear device.