With its fifth - and most powerful - nuclear test since 2006 and the second so far this year, North Korea has shown how far its nuclear weapons programme has come.

More importantly, last Friday's test has experts warning that it would be only a matter of time before the reclusive state perfects the technology to mount a nuclear warhead on a ballistic missile.

It is a scary prospect. Imagine if the North under its volatile leader Kim Jong Un decides to launch a nuclear war against "US-led hostile forces".

Pyongyang has indeed raised the nuclear stakes. The fact that the fifth test came just eight months after the previous one - compared with three years between the third and fourth - is testament that it has accumulated more nuclear material than expected. The latest test coincided with the 68th anniversary of North Korea's founding last Friday.

Concerns are growing in the United States, with media reports noting that the North's accelerated pace of nuclear and missile tests shows its will to threaten the US and its allies South Korea and Japan.

The need for the US to deploy its most powerful Terminal High-Altitude Area Defence anti-missile system in South Korea has become more urgent, despite opposition from China, the North's only ally.

Meanwhile, the United Nations Security Council is mulling over new and tougher punitive sanctions. Seoul is under pressure to rethink its hardline policy against Pyongyang, which critics say has failed to curb the regime's nuclear ambitions.

To foil the North's plans, said US-based Korea expert Jonathan Pollack of the Brookings Institution, the world must move fast in assessing its weapons capabilities, what it could achieve in the long run and the most practicable means of defending the countries under threat. These issues are not new, but the North's continued nuclear and missile testing in recent months has given them "added urgency that cannot be ignored", added Dr Pollack.