North Korea's attempt to launch what appears to be a medium-range Musudan missile has failed on the birthday of founding leader Kim Il-sung, a high-profile misstep after Pyongyang claimed a series of breakthroughs in its nuclear weapons program.

Key points: North Korea fails to launch what appears to be a Musudan-class missile

North Korea fails to launch what appears to be a Musudan-class missile Launch failure occurred on the birthday of founding leader Kim Il-Sung

Launch failure occurred on the birthday of founding leader Kim Il-Sung Musudan missiles are reported to have a range of up to 4,000 kilometres

There had been widespread intelligence reports in recent days that the North was preparing a first-ever flight test of the Musudan, believed to be capable of striking US bases in the Pacific island of Guam.

The US and South Korean militaries both detected and tracked the early morning test.

"We assess that the launch failed," a US defence official said, adding that it was "presumably" a Musudan.

The April 15 birthday of Kim Il-sung — the grandfather of current ruler Kim Jong-un — is a major public holiday in North Korea, where key political anniversaries are often marked with displays of military muscle.

A Pentagon spokesman described the attempted launch as a catastrophic failure.

"I can tell you it was a fiery, catastrophic attempt at a launch that was not successful," Navy Captain Jeff Davis said, adding that the US military was still assessing exactly what happened.

The country is gearing up for a rare and much-hyped ruling party congress next month, at which Kim Jong-un is expected to take credit for pushing the country's nuclear weapons program to new heights.

Pyongyang has hailed a series of achievements in recent months, including miniaturising a nuclear warhead to fit on a missile, developing a warhead that can withstand atmospheric re-entry, and building a solid-fuel missile engine.

Last week, it said it had successfully tested an engine designed for an inter-continental ballistic missile (ICBM) that would "guarantee" an eventual nuclear strike on the US mainland.

A recently released undated photo by KCNA showing the ground jet test of a new high-power engine of inter-continental ballistic rocket designed and produced at the Sohae Space Center in North Pyongan Province. ( AFP: KCNA/KNS )

Outside experts have treated a number of the claims with scepticism, while acknowledging that the North's nuclear and ballistic missile programs have both made significant strides.

If Friday's failure is confirmed as a Musudan test, it would mark a very unwelcome public failure and fuel doubts about just how far the North has gone in developing a reliable nuclear delivery system.

"We are monitoring and continuing to assess the situation," another US official said, calling on North Korea to "refrain from actions that further raise tensions in the region".

Failed launch heightens possibility of further nuclear tests

South Korean officials and international experts said the failed launch heightened the possibility of North Korea conducting another nuclear test, possibly within weeks.

"North Korea is capable of conducting an additional nuclear test at any time if there is a decision by Kim Jong-un," said a senior South Korean official involved in national security policies involving the North.

When asked if the failed missile launch had increased the possibility that Mr Kim would order a nuclear test, the official said the North was likely to "engage in additional provocations."

Anxiety has been high on the divided Korean peninsula since Pyongyang conducted its fourth nuclear test in January and a rocket launch a month later that was widely seen as a disguised ballistic missile test.

The UN Security Council responded with its toughest sanctions to date, angering the North, which has since made repeated threats of attacks targeting the South and the US.

Existing UN resolutions forbid North Korea from the use of any ballistic missile-related technology.

The nuclear-armed state has staged several short- and mid-range missile launches but has yet to test the Musudan, which has an estimated range of anywhere between 2,500 and 4,000 kilometres.

The lower range covers the whole of South Korea and Japan, while the upper range would include US military bases on Guam.

The Musudan was first unveiled as an indigenous missile at a military parade in Pyongyang in October 2010.

Analysis by security consultants IHS Jane's suggests it is an intermediate-range, road-mobile, liquid-propellant, single warhead missile based on the Russian R-27 and using adapted Soviet Scud technology.

Mounted on a wheeled transport-erector-launcher vehicle, it could be fired within 15 minutes of the launcher being positioned and has a potential payload of 1-1.25 tonnes.

AFP/Reuters