Under the right circumstances, terrorists could break into computer systems and launch an attack on a nuclear state, claimed the International Commission on Nuclear Non-proliferation and Disarmament (ICNND).

Cyber-terrorists could provoke a nuclear launch by spoofing early warning and identification systems or by degrading communications networks.

Hackers could also focus on feeding in false information further down the chain – or spreading fake information to officials in a carefully orchestrated strike.

Governments around the world have recently stepped up their commitment to increasing cyber-defence, after a number of high-profile incidents in which hackers launched attacks on foreign nations. Recent online conflicts, as well as reported attacks on government computer systems in the US, UK and elsewhere have increased the stakes.

In Britain, Gordon Brown recently announced plans to step up online intelligence operations – while in the US, President Obama has said he intends to appoint a cyber-security tsar to ensure that protecting America’s computer systems “will be a national security priority”.

The tremor struck at 9:54am (local time), 375 kilometres north-east of Pyongyang at a depth of just 10 kilometres. The Stalinist North last staged a nuclear test in October 2006 but it is believed this blast was much bigger.

The successful nuclear test is greatly inspiring the army and people of the DPRK all out in the 150-day campaign, intensifying the drive for effecting a new revolutionary surge to open the gate to a thriving nation.

The test was staged while South Korea was in mourning for former President Roh Moo-Hyun, who died Saturday after being questioned in a corruption probe.

North Korea carried out what it called a rocket launch on April 5, but the United States, South Korea and Japan said it staged a disguised ballistic missile test.

The US Geological Survey said it detected what it called a 4.7-magnitude earthquake in North Korea.