South Korea confirmed, the failure of a North Korean missile launch would mark another setback for a weapons programme that ultimately aspires to develop a proven nuclear strike capability against the US mainland.
UN resolutions ban North Korea from any use of ballistic missile technology and, just hours before Wednesday's launch effort, the Pentagon had warned Pyongyang against pressing ahead with any missile test.
A defence ministry official in Seoul said the North fired what was believed to be a medium-range Musudan missile off its east coast.
"The launch appears to have failed," the official said, without elaborating.
The North has made four previous failed attempts this year to test fly 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.
First unveiled as an indigenous missile at a military parade in Pyongyang in October 2010, the Musudan has never been successfully flight-tested.
Three failures in April were seen as an embarrassment for North Korea's leadership, coming ahead of a rare ruling party congress that was meant to celebrate the country's achievements.
Another attempt in May was also deemed to have failed.
Wednesday's effort came with military tensions still running high following Pyongyang's fourth nuclear test in January and a long-range rocket launch a month later that saw the UN Security Council impose its toughest sanctions to date on the North.
During the party congress in May, North Korean leader Kim Jong-Un had personally extended an offer of military dialogue with the South.
The proposal was repeated several times by the North's military, but Seoul dismissed all the overtures as insincere "posturing" given Kim's vow at the same congress to push ahead with the country's nuclear weapons programme.
In recent months, North Korea has claimed a series of technical breakthroughs in developing an intercontinental ballistic missile (ICBM) capable of delivering a nuclear warhead to targets across the continental United States.
The claimed achievements included 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.
The North also hailed the successful test of an engine specifically designed for an ICBM that would "guarantee" an eventual nuclear strike on the US mainland.
Outside experts have treated a number of the claims with scepticism, while acknowledging that the North has made significant strides in upgrading its nuclear arsenal.
