North Korea warned its tough-talking neighbor on Sunday against holding more firing drills near a disputed maritime border off the west coast of the peninsula, accusing the South of being "hell-bent to set off a war."
Seoul has sharply increased its rhetoric over the past week, prompted by growing protests and public opinion polls critical of the conservative government's perceived weak response to last month's deadly shelling of Yeonpyeong island.
South Korea's military says it is preparing to stage more live-fire drills in the disputed area, possibly as soon as Monday, enraging Pyongyang, which said last month's attack was set off by a similar drill when the South fired artillery shells into its waters.
The South said those drills were harmless and regular, and that they were conducted on its side of the so-called Northern Limit Line (NLL).
Tensions have risen to their highest level in decades on the divided peninsula after the attack, which came days after the North's revelation it had made significant advances in its nuclear programme.
The foreign ministers of South Korea and Japan on Sunday left for Washington to meet Secretary of State Hillary Clinton to discuss North Korea. They are expected to produce a statement condemning Pyongyang's actions.
China, the North's only major ally and the chair of stalled international nuclear talks with Pyongyang, is not invited. However, the Washington troika are expected to discuss Beijing's proposal for emergency regional talks on the crisis.
North Korea disputes the NLL near Yeonpyeong, a sea border established by the United Nations, without Pyongyang's consent, at the end of the 1950-53 Korean War.
The South is "loudly advertising that they would fire shells into the territorial waters of the DPRK side from Yeongpyeong island, i.e. in the same direction they did when committing the recent provocation," the North's KCNA state news agency reported.
"This indicates how frantic they have become in their provocative acts ... (the South) is so hell-bent on the moves to escalate the confrontation and start a war that it is behaving recklessly, bereft of reason," it said.
The South's new Defense Minister Kim Kwan-jin has vowed to hit back hard against the North if provoked again, saying Seoul will respond with bombs and air power next time.
The South's leaders say they expect the North will stage another provocation, continuing its strategy of antagonizing Seoul with small-scale military attacks.
Analysts say they expect the North will stage increasingly bigger actions, but doubt the situation will escalate into a full-scale war. Other measures could include missile and nuclear tests, which have already been punished with U.N. sanctions.
MINISTER DECRIES TEPID RESPONSE
Last month's attack marked a significant upward tick in its provocations as it was the first time the North had hit a civilian area on South Korean soil since the end of the Korean war. Among the four killed were two civilians, and dozens of homes were destroyed.
Defense Minister Kim, a retired general, toured the island dressed in fatigues after officially taking office on Saturday.
"This incident happened because our military had responded (to North Korea's actions) in a tepid manner so far," said Kim, who took the job after his predecessor was criticized for not striking back firmly against the North after the sinking of South Korean warship in March and the Yeonpyeong attack.
Analysts say Pyongyang's moves could be driven by a number of factors including internal politics and its time-honored practice of using threats and violence for leverage to win aid at talks.
Two years ago, North Korea walked out of aid-for disarmament talks -- which had brought together the two Koreas, host China, the United States, Japan and Russia.
Pyongyang said its wanted to restart the talks, and has won the backing of Beijing and Moscow, but Washington, Seoul and Tokyo have said they will only return to the negotiating table when the North shows it is sincere about denuclearizing.
After a flurry of diplomatic activity in recent months aimed at restarting the six-party talks, the North criticized Seoul and Washington for refusing to return to dialogue and now believes it may have been rushing the process.
In November, the North revealed it had thousands of operating centrifuges at a uranium enrichment plant, giving it a second route to make an atomic bomb and raising proliferation concerns.
North Korea has conducted two nuclear tests to date and is believed to have enough fissile material from its plutonium-based programme to make between six and 12 bombs.