Washington:Defying global public opinion, reclusive North Korea has claimed to have detonated its first hydrogen bomb sending political shock waves around the world and even angering its ally China.

China joined the US, Russia, the European Union and others in condemning the action as a breach of international law and the UN Security Council tentatively scheduled an emergency meeting later on Wednesday at the behest of the US and Japan.

Although North Korea’s claims were taken with a pinch of salt, detection devices around the world recorded a 5.1 seismic event on the country’s northeast coast.

But calling the test a “complete success”, North Korea announced that the test was ordered by its leader Kim Jong-un, who has said for weeks that Pyongyang has the ability to build a thermonuclear weapon.

“If there’s no invasion on our sovereignty we will not use nuclear weapon,” the North Korean state news agency said. “This H-bomb test brings us to a higher level of nuclear power.”

Ned Price, a spokesman for the White House National Security Council, said Washington had not yet determined what kind of test was carried out, but that he expected “North Korea to abide by its international obligations and commitments”.

State Department spokesman John Kirby said “we have consistently made clear that we will not accept” North Korea as a nuclear state.

“We will continue to protect and defend our allies in the region, including the Republic of Korea, and will respond appropriately to any and all North Korean provocations.”

And as Foreign Policy magazine put it, North Korea’s fourth nuclear test since 2006 “hasn’t endeared the North to any potential allies, as both China and Russia have joined the chorus of international condemnation of the test”.

It cited South Korea’s intelligence services and other experts as saying they were sceptical that the test was a hydrogen bomb and going by the yield it looks similar to previous thermonuclear tests carried out by Pyongyang.

North Korea’s “assertion, if true, would dramatically escalate the nuclear challenge from one of the world’s most isolated and dangerous states,” said the New York Times.

According to experts cited by Time magazine, the three previous tests, including the most recent underground explosion in 2013, were of an atomic weapon, not the exponentially more devastating hydrogen variety. The other two tests were conducted in 2006 and 2009.

CNN cited David Albright, a former UN weapons inspector, as telling it last year that North Korea could already have 10 to 15 atomic weapons, and that it could grow that amount by several weapons per year.

Albright said he believed Pyongyang had the capability to miniaturise a warhead for shorter missiles, but not yet for intercontinental ballistic missiles capable of reaching the US.