North Korea has said it successfully tested a hydrogen bomb designed to be mounted on its newly developed intercontinental ballistic missile (ICBM), producing a greater yield than any of its previous nuclear tests.

Key points: Previous recent tremors in North Korea have been caused by nuclear tests

Previous recent tremors in North Korea have been caused by nuclear tests Tremor came hours after state media said Kim Jong-un inspected new hydrogen bomb

Tremor came hours after state media said Kim Jong-un inspected new hydrogen bomb Witnesses on the Chinese side of the border said tremor lasted roughly 10 seconds

The hydrogen bomb test ordered by leader Kim Jong-un was a "perfect success" and was a "meaningful" step in completing the country's nuclear weapons programme, according to state television.

The announcement came hours after a large quake that appeared to be man-made was detected near the North's known nuclear test site, indicating that the reclusive country had conducted its sixth nuclear test since 2006.

The tremor struck within a kilometre of the site of a magnitude-5.3 "nuclear explosion" from September last year, according to the United States Geological Survey (USGS).

South Korea said this most recent test appeared to be several times stronger than its previous test, estimating the nuclear blast yield was between 50 to 60 kilotons — or five to six times stronger than the North Korea's fifth test a year ago.

The USGS said the tremor was felt within a kilometre of a "nuclear explosion" from September of 2016. ( Supplied: USGS )

Foreign Minister Julie Bishop's office reiterated the need for sanctions on North Korea in the wake of the test.

"The reports are deeply concerning and only serve to emphasise the importance of using sanctions to compel North Korea to abandon its illegal programs and reinforce our determination in working with our allies and partners to deter Pyongyang from threatening its neighbours," a statement read.

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It is bound to increase the tension hours after United States President Donald Trump and Japanese Prime Minister Shinzo Abe talked by phone about the "escalating" nuclear crisis.

Mr Abe said Japan was speaking to other nations about how to respond.

"I have already instructed the related ministries to collect and analyse intelligence, to keep the people of Japan informed appropriately, as well as to liaise with the related nations such as the US, South Korea, China and Russia," he said.

"It is absolutely unacceptable if North Korea did force another nuclear test, and we must protest strongly.

"We will hold National Security Council from now on to centralise and analyse intelligence."

Witnesses in the Chinese city of Yanji, on the border with North Korea, said they felt a tremor that lasted roughly 10 seconds, followed by an aftershock.

The hydrogen bomb report by North Korea's official KCNA news agency comes amid heightened regional tension following Pyongyang's two tests of ICBMs in July that potentially could fly about 10,000 kilometres, putting many parts of the mainland US within range.

Under third-generation leader Mr Kim, North Korea has been pursuing a nuclear device small and light enough to fit on a long-range ballistic missile, without affecting its range and making it capable of surviving re-entry into the Earth's atmosphere.

North Korea, which carries out its nuclear and missile programmes in defiance of United Nations Security Council resolutions and sanctions, "recently succeeded" in making a more advanced hydrogen bomb that will be loaded on to an ICBM, KCNA said.

Bomb capable of 'great destructive power', state media says

As part of North Korea's work to build an arsenal of viable nuclear ICBMs that can reach the US mainland, Mr Kim inspected the loading of a "homemade" H-bomb into an ICBM during a visit to the North's Nuclear Weapons Institute.

KCNA said the power of the bomb was adjustable from tens to hundreds of kilotons.

"[It] is a multi-functional thermonuclear nuke with great destructive power, which can be detonated even at high altitudes for super-powerful EMP (electromagnetic pulse) attack according to strategic goals," KCNA said.

The North Korean leader has bragged about the country's nuclear capabilities. ( AP/KCNA )

KCNA quoted Mr Kim as saying the process would enable "the country to produce powerful nuclear weapons, as many as it wants".

North Korea in July conducted its first ever ICBM tests, part of a stunning jump in progress for the country's nuclear and missile program since Mr Kim rose to power following his father's death in late 2011.

Tensions on the Korean Peninsula have been high since last month when North Korea threatened to launch missiles into the sea near the strategically located US Pacific territory of Guam after Mr Trump said Pyongyang would face "fire and fury" if it threatened the US.

North Korea further raised regional tensions on Tuesday by launching an intermediate-range ballistic missile over Japan, drawing international condemnation.

The key question is how far North Korea has gotten in efforts to consistently shrink down nuclear warheads so they can fit on long-range missiles.

South Korea's main spy agency has previously asserted that it does not think Pyongyang currently has the ability to develop miniaturised nuclear weapons that can be mounted on ballistic missiles.

Some experts think the North may have mastered this technology.

North Korea is thought to have a handful of rudimentary nuclear bombs and has spent decades trying to perfect a multistage, long-range missile to eventually carry smaller versions of those bombs.

North Korea says its ICBM capabilities have grown recently. ( AP/KCNA (file photo) )

AP/Reuters