Undeterred by North Korea's apocalyptic threats of nuclear war, a daily convoy of tour coaches still happily wends its way to the Demilitarised Zone (DMZ) which separates the two Koreas.

For some foreign visitors, the hot rhetoric has even become a white-knuckle incentive to travel to the heavily fortified border, a major tourist attraction and a vestige of the 1950-53 Korean War.

"It's getting a lot of attention around the world, and it's really exciting to be a part of that and see it first hand," said Shan Shan Loh, a tourist from Malaysia.

Luis Andrade, an engineer from Venezuela, was equally enthusiastic.

"This is the closest I've been to a Cold War situation," Andrade said.

"I've been to Berlin but long after the wall fell. This is like a live Berlin Wall."

When foreign tourists visit Panmunjom on the South-North Korean border they are subject to a host of rules on how they must behave, one of which clearly states: "No scoffing".

As North Korea's propaganda machine has entered near-absurdist overdrive in recent weeks, the temptation to have a little scoff -- and risk the ire of the North's poker-faced guards -- may be hard to resist.

Ten days ago, the North declared it had entered a "state of war" with the South, and on Tuesday it warned of "thermo-nuclear war" and advised foreign tourists to consider fleeing the country.

But experts say it is nowhere near developing an advanced nuclear device and both citizens and foreigners in South Koreas have shrugged off the threat.

"The North Koreans are just trying to scare people and make them nervous," said one tour operator, who added that visitor numbers had shown little deviation from seasonal norms.

"Out of an original group of 43, we had two cancel today, but that's rare," the operator said.

"We don't do what (North Korean leader) Kim Jong-Un tells us. We stay calm and steady.

"If there was any real safety fear, the UN would cancel the tours. We follow their lead," she said.

A long queue stretched out from the entrance of one of the tour highlights -- a secret invasion tunnel dug by North Korea and discovered by the South in 1978.

The tunnel is a reminder of a time when North-South tensions were more about action than rhetoric and is an impressive feat of engineering, dug at a depth of about 75 metres (250 feet).

Apparently designed for a surprise attack on Seoul, an estimated 30,000 men with light weaponry could move through the tunnel in an hour.

The main draw of the tour is Panmunjom, the abandoned border village where the armistice that ended the Korean War was signed and where guards from North and South now eyeball each other at close proximity.

A month ago, Pyongyang announced it was unilaterally ripping up the armistice, but the guards have continued to exchange nothing more physical than cold stares.

Prior to touring Panmunjom, tourists must sign a "visitor declaration" which, as well as ruling out scoffing, prohibits pointing and gesturing.

"If any incidents should occur, remain calm," reads the declaration which also requires the signatory to waive any right to compensation for any "damage of body" resulting from the visit.

Most tourists sign after just a cursory glance.

Guide duties at Panmunjom are mainly performed by a designated UN Security Escort Specialist, one of whom said the heightened tensions had a limited impact on those serving at the border.

"Or on us, at least. If the North did something to the UN its like declaring war on the world. The South Korean forces probably feel the tension more," he said.

N. Korea urges foreigners in South to evacuate
Seoul (AFP) April 09, 2013 - North Korea said Tuesday the Korean peninsula was headed for "thermo-nuclear" war and advised foreigners to consider leaving South Korea, as the UN chief warned of a potentially "uncontrollable" situation.

Tuesday's advisory -- greeted largely with indifference -- followed a similar one last week to foreign embassies in Pyongyang, to consider evacuating by April 10 on the grounds war may break out.

"The situation on the Korean Peninsula is inching close to a thermo-nuclear war," the 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".

The committee blamed the heightened war risk on the "warmongering US" and its South Korean "puppets" who were intent on invasion.

White House spokesman Jay Carney criticised Pyongyang for more "unhelpful rhetoric that serves only to escalate tensions".

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.

"It is our current assessment that there is no immediate risk to British nationals in South Korea," a British embassy spokesman said, echoing similar statements from the US, French and other missions.

Last week's warning to embassies in Pyongyang was also largely dismissed as empty rhetoric, with most governments making it clear they had no plans to withdraw personnel.

Breaking with international efforts to play down the threats, one South Korea lawmaker said Tuesday that Seoul had the right to withdraw from the Non-Proliferation Treaty and to match North Korea's nuclear work step-by-step.

Chung Mong-Joon, a billionaire businessman who belongs to the ruling conservative New Frontier Party, said on a visit to Washington that the latest crisis with North Korea showed that diplomacy had failed with Pyongyang.

"It would send a clear warning that, by continuing its nuclear programme, North Korea is releasing the nuclear genie in East Asia," Chung told a conference of the Carnegie Endowment for International Peace.

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 Korean-US military exercises.

Yonhap news agency Tuesday cited South Korean intelligence as saying the North had completed preparations for an expected missile test-launch -- possibly to coincide with April 15 celebrations for the birthday of late founder Kim Il-Sung.

Japan, where the armed forces have been authorised to shoot down any North Korean missile headed towards its territory, said Tuesday it had deployed Patriot missiles in its capital as a pre-emptive defence measure.

A top US military commander said Tuesday that he favoured shooting down a North Korean missile only if it threatened the United States or Washington's allies in the region.

UN Secretary General Ban Ki-moon said during a visit to Rome he had spoken to the Chinese leadership to try to calm tensions, and would discuss the issue with US President Barack Obama on Thursday.

"The current level of tension is very dangerous, a small incident caused by miscalculation or misjudgement may create an uncontrollable situation," he said.

However Tuesday's threat was unlikely to worry South Korea's 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.

The North announced Monday it was taking the unprecedented step of pulling out its 53,000 workers and shutting the complex down indefinitely.

Established in 2004, Kaesong has never closed before. Pyongyang's move reflects the depth of the current crisis, which has otherwise been notable more for fiery rhetoric than action.

Kaesong, 10 kilometres (six miles) inside North Korea, is a crucial hard currency source for the impoverished North, mainly through its cut of the workers' wages.

South Korean President Park Geun-Hye said the North's action was "very disappointing" and displayed a total disregard for investment norms that would return to haunt Pyongyang in the future.