North Korea said Tuesday the Korean peninsula was headed for "thermo-nuclear" war and advised foreigners in South Korea to consider evacuation, in the latest in a series of apocalyptic threats.
It followed a similar warning issued last week to foreign embassies in its capital Pyongyang to consider evacuating by April 10, saying it could not ensure the safety of their personnel if a conflict broke out.
"The situation on the Korean Peninsula is inching close to a thermonuclear war," the North's Asia-Pacific Peace Committee said in a statement carried by the North's official Korean Central News Agency.
Saying it did not want to see foreigners in South Korea "fall victim", the statement requested all foreign institutions, enterprises and tourists "to take measures for shelter and evacuation in advance for their safety".
The committee blamed the heightened war risk on the "warmongering US" and its South Korean "puppets" who were intent on invading the North.
The "thermo-nuclear war" threat has been wielded several times in recent months -- most recently on March 7 -- despite expert opinion that North Korea is nowhere near developing such an advanced nuclear device.
Last week's warning to embassies was also largely dismissed as empty rhetoric, with most governments involved making it clear they had no plans to withdraw personnel from their Pyongyang missions.
"It's almost comic," Daniel Pinkston, a North Korea expert with the International Crisis Group, said of the latest threat.
"They want to rattle the investment market, create pressure and make people nervous.
"But it's just not working. It's as if they didn't get a rise out of the embassies in Pyongyang, so they're just moving on to the next target," Pinkston said.
The South Korean stock market closed slightly up Tuesday, before the KCNA statement was published.
The Korean peninsula has been locked in a cycle of escalating military tensions since the North's third nuclear test in February, which drew toughened UN sanctions.
Pyongyang's bellicose rhetoric has reached fever pitch in recent weeks, with near-daily threats of attacks on US military bases and South Korea in response to ongoing South Korea-US military exercises.
There has been no significant foreign investment fallout in South Korea from the current crisis, and Tuesday's threat was unlikely to cause any great consternation for a foreign community of around 1.4 million that has calmly weathered the rhetorical storm thus far.
Earlier Tuesday, North Korean workers followed Pyongyang's order to boycott the Kaesong joint industrial zone with South Korea, signalling the possible demise of the sole surviving symbol of cross-border reconciliation.
"Not a single worker showed up this morning," the manager of one of the 123 South Korean companies operating in Kaesong told reporters.
The North announced Monday it was taking the unprecedented step of pulling out its 53,000 workers and shutting the complex down indefinitely, following a tour of the zone by senior ruling party official Kim Yang-Gon.
Established in 2004, Kaesong has never been closed before. Pyongyang's move reflects the depth of the current crisis on the Korean peninsula, which has otherwise been more notable for fiery rhetoric than action.
Located 10 kilometres (six miles) inside North Korea, Kaesong is a crucial hard currency source for the impoverished North, through taxes and revenues, and from its cut of the workers' wages.
Turnover in 2012 was reported at $469.5 million, with accumulated turnover since 2004 standing at $1.98 billion.
South Korean President Park Geun-Hye said the North's action on Kaesong was "very disappointing" and displayed a total disregard for investment norms that would return to haunt Pyongyang in the future.
"If North Korea, under the full eyes of the international community, breaches international rules and promises like this, then there will be no country or company which will invest in North Korea," Park said.
Pyongyang has blocked South Korean access to Kaesong since Wednesday, forcing 13 South Korean firms to halt production.
Yu Chang-Geun, vice president of the association representing the South's companies, said operations would have to be normalised swiftly to prevent permanent collateral damage.
"All firms have reached their limit. If things go on like this, all of us will face bankruptcy," Yu said.
More than 300 South Korean workers have left Kaesong and returned to the South since North Korea banned access last week.
Of the 475 remaining, the Unification Ministry said 77 had signed up to leave on Tuesday.
Japan has deployed Patriot missiles in its capital as it readies to defend the 30 million people who live in greater Tokyo from any North Korean attack, officials said Tuesday.
Two Patriot Advanced Capability-3 surface-to-air missile launchers were stationed at the defence ministry in Tokyo before dawn, a ministry spokesman said, while Defence Minister Itsunori Onodera said "we are proceeding with measures including deployment of PAC-3 as we are on alert".
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