The nuclear-armed North is under several sets of United Nations sanctions over its atomic and ballistic missile programmes.
It is on a quest to develop a long-range missile capable of hitting the US mainland with an atomic warhead, and staged two nuclear tests and multiple missile launches last year.
The North fired one missile from an air base in the eastern port of Wonsan Wednesday morning, but the launch "is believed to have failed", Seoul's defence ministry said in a statement, adding it was analysing what type of missile was involved.
The US military said the missile exploded shortly after launch.
"US Pacific Command detected what we assess was a failed North Korean missile launch attempt... in the vicinity of Kalma. A missile appears to have exploded within seconds of launch," said spokesman David Benham.
Earlier this month Pyongyang launched a flight of four ballistic missiles, with three landing provocatively close to Japan in what the North described as practice for attacks on US military bases in Japan.
On Sunday, its leader Kim Jong-Un personally oversaw and hailed a "successful" test of what Pyongyang said was a new rocket engine -- which can be easily repurposed for use in missiles.
Seoul said that experiment showed "meaningful progress" in the North's missile capabilities.
The developments come as Seoul and Washington hold large-scale annual joint military exercises that always infuriate Pyongyang, which sees them as a rehearsal for invasion.
Analysts' opinions are varied on how advanced the North's missile technologies are but many agree that Pyongyang has made significant progress in recent years.
'Option on the table'
Sunday's engine test was apparently timed to coincide with a recent Asia trip by new US Secretary of State Rex Tillerson, who warned that regional tensions had reached a "dangerous level".
Washington would drop the "failed" approach of "strategic patience" with Pyongyang, Tillerson said, warning that US military action was an "option on the table" if necessary -- a sharp divergence from China's insistence on a diplomatic approach to its neighbour, which it has long protected.
This week the North's state news agency KCNA boasted that Tillerson had "admitted the failure" of US policy to denuclearise the nation.
Pyongyang insists that it needs nuclear weapons for self-defence against "hostile enemies" including the South and its ally the US.
But it has yet to test an inter-continental ballistic missile (ICBM) capable of flying across the Pacific Ocean.
The country's long-range Musudan device has a theoretical range of anywhere between 2,500 and 4,000 kilometres (1,500 and 2,500 miles). The lower estimate covers the whole of South Korea and Japan, while the upper range would include US military bases in Guam.
The missile was tested eight times last year -- but only one of those was successful, with the others exploding in mid-air shortly after launch.
A Musudan launched in June last year flew 400 kilometres off the east coast of the peninsula and was hailed by Kim as proof of the North's ability to strike US bases across the "Pacific operation theatre".
The New York Times reported earlier this month that under former president Barack Obama the US stepped up cyber attacks against North Korea to try to sabotage its missiles before launch or just as they lift off.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)