South Korea will strike back quickly if the North stages any attack, the new president in Seoul warned on Monday, as tensions ratcheted higher on the Korean peninsula amid shrill rhetoric from Pyongyang and the US deployment of radar-evading fighter planes.
North Korea says the region is on the brink of a nuclear war in the wake of United Nations sanctions imposed for its February nuclear test and a series of joint US and South Korean military drills that have included a rare US show of aerial power.
The North, whose economy is smaller than it was 20 years ago, appeared to move on Monday to addressing its pressing need for investment by appointing a reformer to the country's ceremonial prime minister's job, although the move mostly cemented a power grab by the ruling Kim clan.
North Korea had said on Saturday it was entering a "state of war" with South Korea in response to what it termed the "hostile" military drills being staged in the South.
But there have been no signs of unusual activity in the North's military to suggest an imminent aggression, a South Korean defence ministry official said last week.
"If there is any provocation against South Korea and its people, there should be a strong response in initial combat without any political considerations," President Park Geun-hye told the defence minister and senior officials at a meeting on Monday.
The South has changed its rules of engagement to allow local units to respond immediately to attacks, rather than waiting for permission from Seoul.
Stung by criticism that its response to the shelling of a South Korean island in 2010 was tardy and weak, Seoul has also threatened to target North Korean leader Kim Jong-un and to destroy statues of the ruling Kim dynasty in the event of any new attack, a plan that has outraged Pyongyang.
Seoul and its ally the United States played down Saturday's statement from the official KCNA news agency as the latest in a stream of tough talk from Pyongyang.
North Korea stepped up its rhetoric in early March, when US and South Korean forces began annual military drills that involved the flights of US B-2 stealth bombers in a practice run, prompting the North to puts its missile units on standby to fire at US military bases in the South and in the Pacific.
The United States also deployed F-22 stealth fighter jets on Sunday to take part in the drills. The F-22s were deployed in South Korea before, in 2010.
On its part, North Korea has cancelled an armistice agreement with the United States that ended the Korean War and cut all hotlines with US forces, the United Nations and South Korea.
Nuclear weapons "not a bargaining chip"
Park's intervention came on the heels of a meeting of the North's ruling Workers Party Central Committee where leader Kim Jong-un rejected the notion that Pyongyang was going to use its nuclear arms development as a bargaining chip.
"The nuclear weapons of Songun Korea are not goods for getting US dollars and they are ... (not) to be put on the table of negotiations aimed at forcing the (North) to disarm itself," KCNA news agency quoted him as saying.
At the meeting, Kim appointed a handful of personal confidants to the party's politburo, further consolidating his grip on power in the second full year of his reign.
The most surprising appointment came on Monday as former prime minister Pak Pong-ju was re-appointed as premier, although the move likely signalled another power struggle in Pyongang staged by the country's leader Kim Jong-un.
Pak is viewed as a key ally of Jang Song-thaek, the young Kim's uncle and also a protege of Kim's aunt and is viewed as a pawn in a power game that has seen Jang and his wife re-assert power over military leaders.
Analysts said the move would not likely change Pyongyang's approach to a confrontation that appears to have dragged the two Koreas closer to war.
Pyongyang's on-off negotiations saw it take part in nuclear disarmament talks for five years aimed at paying it off in return for abandoning its atomic weapons programme.
Those talks fell apart in 2008. Some experts say the talks gave the North grounds to pursue a highly enriched uranium programme that took it closer to owning a working arsenal.
Songun is the Korean word for the "Military First" policy preached by Kim's father who used it to justify the use of the impoverished state's scare resources to build a 1.2-million strong army and a weapons of mass destruction programme.
Calls for restraint
White House National Security Council spokeswoman Caitlin Hayden said North Korea's announcement that it was in a state of war followed a "familiar pattern" of rhetoric. China has repeatedly called for restraint on the peninsula.
However, many in South Korea have regarded the North's willingness to keep open the Kaesong industrial zone, located just a few miles (km) north of the heavily-militarised border and operated jointly by both sides, as a sign that Pyongyang will not risk losing a lucrative source of foreign currency.
Closure could also trap hundreds of South Korean workers and managers of the more than 100 firms that have factories there.