|North Korea's nuclear and missile tests have raised tensions across northeast Asia [AFP]
North Korea's second nuclear test has sent shockwaves through northeast Asia, catching many of its neighbours off guard and raising questions over the future stability of the region.
Here we take a look at how Japan, South Korea and China see the changing regional security framework.
After twice firing long-range rockets through Japan's airspace, the recent escalation in military posturing by North Korea has once again rattled Japanese nerves.
|Some in Japan are calling for a new more pre-emptive military strategy [EPA]
Japan and the Korean peninsula have a troubled history, particularly related to the brutal occupation of Korea by the Japanese imperial army in the run-up to and during the second world war.
Now North Korea's nuclear and missile tests have reignited a sensitive debate in Japan over strengthening the country's armed forces.
Japan is due to release new national defence guidelines later this year and some are calling for fundamental changes to the country's post-war pacifist constitution.
In particular questions are being asked about whether the military, which is barred from offensive action, should be allowed to carry out pre-emptive strikes against perceived imminent threats.
Some are even calling for Japan, the only country in history to have suffered nuclear attack, to develop its own nuclear weapons.
Given its advanced civilian nuclear energy programme it has been widely accepted that - should it take the decision to go nuclear - Japan could build a weapon within as little as six months.
At the moment Japan has no so-called power projection weapons – systems such as aircraft carriers, long-range missiles or other weapons that allow it to project force well beyond its borders.
But calls are growing in some quarters for Japan's exclusively defence-oriented military posture to change.
One former Japanese defence chief has said the country needs to take a more proactive stance and should not be in a position to "sit and wait for death".
For many of Japan's regional neighbours the prospect of a militarily resurgent Japan, perhaps one armed with nuclear weapons, revives troubling memories of the country's wartime past.
Since the end of the Korean war more than half a century ago, South Koreans have lived with the threat that the war with their northern neighbour could once again turn hot.
|South Korea's military are on a constant state of alert over the threat from the North [EPA]
On near-constant alert against the North's 1.2 million-strong army, South Korea has an armed forces of about 687,000, backed up by around 28,000 US personnel stationed in the country.
While in terms of simple manpower the odds would appear to be stacked in North Korea's favour, analysts say there is little doubt the technologically superior South Korean and US forces would prevail in the event of conflict.
Nonetheless any war on the Korean peninsula would come at a terrible price.
Seoul, the South Korean capital, lies less than 60km from the heavily-fortified "demilitarised zone" that divides the two Koreas.
On the other side of the zone, hundreds of North Korean artillery and rocket batteries stand ready to make good on the North's threat to turn Seoul into "a sea of ashes".
For half a century most South Koreans have felt secure enough under the pledge of US security guaranties.
But with North Korea now rattling its nuclear sabre louder than ever, there is also the prospect that a jittery South Korea may be persuaded to develop its own nuclear arsenal – particularly if Japan also opts to go down the nuclear path.
In 2004 South Korea admitted that its scientists had produced a small amount of near-weapons grade uranium four years earlier, raising the prospect that it would not be that far of a technical leap for the South to develop its own bomb.
At the time the government said the material, amounting to less than a gram in weight, was produced by a group of rouge scientists operating without official approval.
But questions remain over the laser enrichment technique the scientists had apparently used – a technique so expensive that most experts say its only utility would be would be for military purposes.
For years China has been North Korea's biggest supplier of aid and has been seen as the closest the reclusive country has to an ally.
|China is finding that its influence over North Korea has waned [Reuters]
It is North Korea's biggest trade partner by far, with Chinese loans accounting for much of the rest of North Korea's imports - effectively propping up the North Korean economy
China, which has its own nuclear arsenal, is believed to have had some role in training North Korean nuclear engineers, although its association with the North's weapons programme is extremely murky.
But recent developments have shown that even China has little real ability to keep a tight rein on its unpredictable neighbour.
For years China has advocated cautious diplomacy as the best way of dealing with North Korea.
Beijing brokered the six-nation disarmament talks, and has revived them several times from the brink of collapse.
But with North Korea now having walked away from those talks vowing never to return, Chinese officials are becoming increasingly impatient with their troublesome ally.
China has traditionally been wary of any moves that could push the North Korean regime to collapse – a move that could potentially send millions of refugees streaming across its borders.
Now it has to balance that fear with the prospect of a regional arms race and a bellicose North Korea triggering Japan to rebuild its own armed forces.