North Korean leader Kim Jong-Un personally signed the order three weeks ago authorising Pyongyang’s latest nuclear test, calling for 2016 to kick off with the “thrilling sound” of a hydrogen bomb explosion.

The North said on Wednesday it had conducted its first “successful” miniaturised hydrogen bomb test — a shock announcement that drew condemnation from its neighbours including its major ally China.

The news was broadcast on state television, which also showed a copy of Kim’s initial signed order dated 15 December.

“Let’s begin the year of 2016 … with the thrilling sound of our first hydrogen bomb explosion, so that the whole world will look up to our socialist, nuclear-armed republic and the great Workers’ Party of Korea!” Kim wrote in a handwritten message next to his signature.

The television also showed a second order dated 3 January in which Kim signed off his final approval for the test to be conducted on 6 January.

Kim, who took over after the death of his father Kim Jong-Il in December 2011, also presided over the country’s third nuclear test in February 2013.

A hydrogen, or thermonuclear, bomb uses fusion in a chain reaction that results in a far more powerful explosion than the fission blast generated by uranium or plutonium alone.

North Korea was believed to be years from developing such a sophisticated device, and experts voiced scepticism that Wednesday’s test was indeed of a hydrogen bomb — saying the apparent yield was far too low.

Kim had suggested last month Pyongyang had already developed such an H-bomb — a claim that was largely dismissed as exaggerated rhetoric at the time.