South Korea have developed what they are calling a blackout bomb that would wipe out North Korean electricity without killing anyone if Kim Jong-un tried to attack.

The bomb, which Seoul says can be built at any time, would paralyse the hermit nation if it were deployed.

The graphite bomb would cover Pyongyang's electrical facilities in carbon graphite filaments which would shut down the country's power grid and nullify its nuclear threat.

The graphite bomb, which Seoul says can be built at any time and a version of which is picture here, would paralyse the hermit nation if it were deployed

The graphite bomb would cover Pyongyang's electrical facilities in carbon graphite filaments which would shut down the country's power grid and nullify its nuclear threat

Kim Jong-un (pictured) said his nuclear weapons were a 'powerful deterrent' that guaranteed its sovereignty, state media reported on Sunday, hours after US President Donald Trump said 'only one thing will work' in dealing with the isolated country

A South Korean military spokesman told the country's Yonhap news agency: 'All technologies for the development of a graphite bomb led by the Agency for Defence Development have been secured.

'It is in the stage where we can build the bombs anytime.'

While nuclear war would likely cause millions of deaths, the South Korean approach would not target any civilians.

The graphite bomb is a non-lethal weapon containing filaments which unleash a thick cloud when it explodes.

Carbon fibres in the cloud cling to power lines, causing grids to short circuit and cut out.

The graphite bomb can be countered by insulated power cables, and electricity would reboot once the cloud dispersed, meaning it would only be a temporary defence measure against Kim Jong-un's nuclear threat.

The dictator said his nuclear weapons were a 'powerful deterrent' that guaranteed its sovereignty, state media reported on Sunday, hours after US President Donald Trump said 'only one thing will work' in dealing with the isolated country.

Trump did not make clear to what he was referring, but his comments seemed to be a further suggestion that military action was on his mind.

The test launch of an intermediate range Hwasong-12 in North Korea

In a speech to a meeting of the powerful Central Committee of the ruling Workers' Party on Saturday, a day before Trump's most recent comments, state media said Kim had addressed the 'complicated international situation'.

North Korea's nuclear weapons are a 'powerful deterrent firmly safeguarding the peace and security in the Korean peninsula and Northeast Asia,' Kim said, referring to the 'protracted nuclear threats of the US imperialists'.

In recent weeks, North Korea has launched two missiles over Japan and conducted its sixth nuclear test, and may be fast advancing toward its goal of developing a nuclear-tipped missile capable of hitting the US mainland.

North Korea is preparing to test-launch such a missile, a Russian lawmaker who had just returned from a visit to Pyongyang was quoted as saying on Friday.

Donald Trump has previously said the United States would 'totally destroy' North Korea if necessary to protect itself and its allies.

The situation proved that North Korea's policy of 'byungjin', meaning the parallel development of nuclear weapons and the economy was 'absolutely right', Kim Jong-un said in the speech.

'The national economy has grown on their strength this year, despite the escalating sanctions,' said Kim, referring to U.N. Security Council resolutions put in place to curb Pyongyang's nuclear and missile programmes.