North Korea has become a "global threat" after its latest nuclear test, the UN's nuclear watchdog has said.

The North's claim it had tested a hydrogen bomb represents a "new dimension of threat," Yukiya Amano, director general the International Atomic Energy Authority, told CNN.

"I think the North Korean threat is a global one now. In the past people believed it was a regional one, that's no longer the case," Mr Amano said.

"It is a global threat now and it combines nuclear weapons and missiles."

While the authority said it could not determine whether the explosion came from a hydrogen bomb, as North Korea claimed, Mr Amano said the test's bigger yield means "it is safe to assume North Korea is making significant progress."

Kim Jong-un inspects weapon North Korea says is powerful hydrogen bomb Show all 6 1 /6 Kim Jong-un inspects weapon North Korea says is powerful hydrogen bomb Kim Jong-un inspects weapon North Korea says is powerful hydrogen bomb Photos released by North Korea show Kim Jong-un talking to subordinates next to a device thought to be the new thermonuclear weapon. There is no way of independently verifying the pictures STR/AFP/Getty Images Kim Jong-un inspects weapon North Korea says is powerful hydrogen bomb North Korea claims it has successfully tested an advanced hydrogen bomb which could be loaded onto an intercontinental ballistic missile AFP/Getty Kim Jong-un inspects weapon North Korea says is powerful hydrogen bomb A diagram on the wall behind Mr Kim shows a bomb mounted inside a cone STR/AFP/Getty Images Kim Jong-un inspects weapon North Korea says is powerful hydrogen bomb North Korean leader Kim Jong-Un (C) attending a photo session with participants of the fourth conference of active secretaries of primary organisations of the youth league of the Korean People's Army (KPA) in Pyongyang STR/AFP/Getty Images Kim Jong-un inspects weapon North Korea says is powerful hydrogen bomb A new stamp issued in commemoration of the successful second test launch of the "Hwasong-14" intercontinental ballistic missile KCNA via Reuters Kim Jong-un inspects weapon North Korea says is powerful hydrogen bomb A new stamp issued in commemoration of the successful second test launch of the "Hwasong-14" intercontinental ballistic missile KCNA via Reuters

The UN Security Council has scheduled its second emergency meeting in a week about North Korea after a powerful nuclear test explosion added another layer of urgency for diplomats wrestling with what to do about the North's persistent weapons programmes.

Scheduled after North Korea said it detonated a hydrogen bomb, the emergency session comes six days after the council strongly condemned Pyongyang's "outrageous" launch of a ballistic missile over Japan.

Less than a month ago, the council imposed its stiffest sanctions so far on the reclusive nation.

North Korea is "deliberately undermining regional peace and stability," the council said when it rebuked the missile test, reiterating demands for the country to halt its ballistic missile and nuclear weapons programmes.

Mr Amano added: "North Korea is one of the countries where it's most difficult to guess their next step.

"It's not at the nuclear weapon stage under the treaty but it is clear that North Korea has some nuclear weapons, nuclear explosive devices and missiles.

"In the past the threat of North Korea was related to nuclear weapons. Now the North Korean threat is related to nuclear weapons combined with missiles."