North Korea calls US-South Korea plot a 'declaration of war'

North Korea's UN Mission is calling what it says was a "terrorist" plot by the US and South Korean intelligence agencies to kill leader Kim Jong Un a "declaration of war."

A statement on Thursday from the mission said a "Korean-style anti-terrorist offensive will be commenced to mop up the intelligence and plot-breeding organisations of the US and South Korea."

It reiterated the government's determination "to hunt down and mercilessly smash every single one of the terrorist maniacs of the CIA and the South Korean" Intelligence Service.

The mission urged all UN member states to support North Korea in its efforts. The statement said the organisers infiltrated a "terrorist" into the country who had satellite communications equipment.