No, but it has proved to the world that it has the capability and the technology to produce nuclear warheads, and the clear intention to join the atomic club.

How big was the test?

Reports vary and it will take a few days before experts can be precise about the size of the explosive yield. The Russians, who have carried out hundreds of underground tests and have sophisticated seismic systems to detect clandestine activities in North Korea, claimed that the yield was between five and 15 kilotons, the latter equating to the Hiroshima bomb.

However, the South Koreans said that the blast was equivalent to less than one kiloton of TNT. The South Korean Institute of Geoscience and Mineral Resources estimated the tremor to be about four on the Richter scale, indicating an explosive equivalent to 550 tonnes of TNT, or less than 4 per cent of the power of Hiroshima.

There was even doubt cast on whether it was a nuclear explosion at all, although tests by the Americans, Japanese and Russians over the next few days — including airborne systems that “sniff” out any radioactivity leaked into the atmosphere — will resolve those.

To add to the riddles, Chinese officials close to the North Korean Government claimed that the device tested was a neutron bomb, designed to create massive radioactivity, focusing on killing people rather than destroying whole areas with heat and blast.

How far away is North Korea from developing a complete weapon system — fitting a warhead to a ballistic missile?

Western experts said it was highly unlikely that North Korea would have reached this stage in its clandestine programme without a parallel project to design a warhead for a ballistic missile.

Some observers said that North Korea would face a considerable challenge to design a warhead small enough and robust enough to be fitted to its substantial inventory of short-range and medium-range ballistic missiles. However, Duncan Lennox, Editor of Jane’s Strategic Weapons Systems, said that it would make no sense to carry out a nuclear test without having in mind a specific design for a warhead. Pakistan and India carried out tests eight years ago but had parallel missile programmes, which meant that they became fully-fledged nuclear weapon states in a comparatively short period.

“The North Koreans will have to get the warhead weight down to about 750kg, which is equivalent to second-generation American and Russian nuclear devices,” Mr Lennox told The Times. “That’s not high technology.” A 750kg nuclear warhead would produce a yield of 20-30 kilotons.

Miniaturising nuclear war- heads for intercontinental missiles will be beyond the present North Korean capability. In the most sophisticated weapons- design world, weight does not equate to yield. The Americans and Russians have produced low-weight nuclear warheads capable of producing 250 kilotons.

What missiles do the North Koreans have?

After years of skilfully adapting Russian-made Scud missiles, North Korea has an arsenal of Scud Bs with a range of 320km (200 miles), Scud Cs with a range of 570km, Nodong missiles with a range of about 1,500km and Taepodong 1 missiles with a range of 2,300km. It is researching a system called the Taepodong 2, which could have a range of 15,000km (9,300 miles).

North Korea carried out six missile tests in July, one of them involving the Taepodong 1, which could theoretically reach Alaska and Hawaii, but this launch failed after 40 seconds.

Who has helped North Korea?

Pyongyang has benefited from undercover deals involving Abdul Qadeer Khan, the former Pakistani nuclear weapons chief and so-called father of the Pakistan bomb, who has been accused of masterminding a blackmarket in nuclear weapons trading.

He is suspected of supplying North Korea with uraniumenrichment equipment and possibly even warhead designs, in exchange for Pyongyang’s ballistic missile expertise.

North Korea has developed both an enriched uranium and a plutonium nuclear capability and is believed to be focusing on a plutonium bomb, which is lighter than a uranium device.

WORLD REACTION

‘The Democratic People’s Republic of Korea has ignored the widespread opposition of the international community and brazenly carried out a nuclear test’
Chinese Government

‘This further act of defiance shows North Korea’s disregard for the concerns of its neighbours and the wider international community’
Tony Blair

‘[Japan will] immediately consider taking stern measures’
Shinzo Abe, Japanese Prime Minister

‘Russia absolutely condemns the test in North Korea, which has inflicted great damage to the non-proliferation process’
President Putin

‘North Korea’s nuclear test was a reaction to America’s threats and humiliation’
Iranian state radio

‘Once again, North Korea has defied the will of the international community, and the international community will respond’
President Bush

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