North Korea has threatened to use nuclear weapons
in a "holy war" against its neighbour after South Korean tanks, jets and artillery carried out one of the largest-ever live-fire exercises close to the border.
The exercises at Pocheon, just south of the Demilitarised Zone, were the third such show of force this week by South Korea amid the worst tensions since the 1950-53 war on the peninsula.
Multiple rocket-launchers, dozens of tanks and hundreds of troops joined the exercises which the South Korean president, Lee Myung-bak, insisted were necessary for self-defence, after two deadly attacks this year.
Two civilians and two marines were killed last month by a North Korean barrage of Yeongpyeong island after a live-fire exercise in disputed territory. In March, 46 sailors died when the South Korean ship Cheonan was sunk, apparently by an enemy torpedo.
"We had believed patience would ensure peace on this land, but that was not the case," Lee told troops. He earlierwarned that he was ready to order a "merciless counterattack" if further provoked.
North Korea's armed forces minister, Kim Yong-chun, also lifted the pitch of the sabre-rattling. "To counter the enemy's intentional drive to push the situation to the brink of war, our revolutionary forces are making preparations to begin a holy war at any moment necessary based on nuclear deterrent," the official Korean Central News Agency, quoted him telling a rally in Pyongyang.
Bellicosity and brinkmanship are nothing new on the divided peninsula and there are doubts that North Korea is capable of an accurate nuclear strike, but the situation is less predictable than usual due to the transition of power in Pyongyang from Kim Jong-il to his son, Kim Jong-un. Even with conventional artillery, the two densely populated nations are capable of devastating one another.
Experts believe the restraint shown this week by North Korea may not last if military exercises continue near the border.
"The situation is still a tinderbox. There's still enormous tension, enormous mistrust and I believe diplomacy is what is needed to get us out of this tinderbox," said the governor of New Mexico, Bill Richardson, who has just returned from an unofficial mission to Pyongyang. He described the tensions as "the worst I have ever seen on the peninsula."
Russia has proposed sending a special UN envoy to the region and China has expressed support for a fresh round of six-party denuclearisation talks. But Japan and the US have backed the robust stance taken by Seoul, saying North Korea has not yet done enough to deserve new negotiations.