The reported failed launch on Wednesday came during large-scale annual military drills involving US and South Korean forces that the North has called a rehearsal for an invasion.
Seoul's defence ministry said in a statement that Pyongyang fired one missile from an air base in the eastern port of Wonsan but the launch was believed to had failed.
"We are in the process of analysing what type of missile it was," it added.
The statement came after Japan's Kyodo news service, citing an unidentified government source, said the North might have launched several missiles and that they were a failure.
A US military spokesman also said they had detected a failed North Korean missile launch attempt, with a missile exploding within seconds of its launch.
"US Pacific Command detected what we assess was a failed North Korean missile launch attempt ... in the vicinity of Kalma," Commander Dave Benham, a spokesman for US Pacific Command, said in a statement, referring to an air field on North Korea's east coast.
"A missile appears to have exploded within seconds of launch," Benham said, adding that work was being carried out on a more detailed assessment.
North Korean leader Kim Jong-Un personally oversaw on Sunday a "successful" test of a new rocket engine
The nuclear-armed North is under several sets of United Nations sanctions over its atomic and ballistic missile programmes.
Robert Kelley, a professor of political science and diplomacy at Pusan National University, said Pyongyang often conducts missile tests during the spring military drills carried out by South Korean and US troops.
"This is how the North Koreans send us a signal of displeasure," he told Al Jazeera. "That's what we assume of course, since they don't tell us."
Earlier this month, the isolated country launched a flight of four ballistic missiles, with three landing close to Japan in what Pyongyang described as practice for attacks on US military bases in Japan.
On Sunday, the North's 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 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.