North Korean state media called it a “successful test of great significance” but did not specify what was tested.
South Korea’s joint chiefs of staff, which usually issues alerts if a missile is seen launching from North Korea, declined to comment.
Missile experts said it appeared likely the North Koreans had conducted a static test of a rocket engine, rather than a missile launch.
“If it is indeed a static engine test for a new solid or liquid fuel missile, it is yet another loud signal that the door for diplomacy is quickly slamming, if it isn’t already,” said Vipin Narang, a nuclear affairs expert at the Massachusetts Institute of Technology.
“This could be a very credible signal of what might await the world after the New Year.”
Tensions have risen ahead of a year-end deadline set by North Korea, which has called on the US to change its policy of insisting on Pyongyang’s unilateral denuclearisation and demanded relief from punishing sanctions.
On Saturday, North Korea’s ambassador to the United Nations said denuclearisation was now off the negotiating table with the US and lengthy talks with Washington are not needed.
“The results of the recent important test will have an important effect on changing the strategic position of the DPRK (Democratic People’s Republic of Korea) once again in the near future,” North Korean state media reported.
