North Korea has carried out a "very important" test at its Sohae satellite launch site, state media KCNA reported on Sunday, a rocket testing ground that US officials once said North Korea had promised to close.
The reported test comes as a year-end deadline North Korea has imposed nears, warning it could take a "new path" amid stalled denuclearization talks with the United States.
The KCNA report 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.
Analysts have said the site has never before been used to launch an intercontinental ballistic missile, but it has been used to test missile engines. Past satellite launches have helped scuttle talks with the United States.
Missile experts said it appeared likely the North Koreans had conducted a static test of a rocket engine, rather than a missile launch.
"This is likely a ground-based engine test at the Sohae test stand. This is 'not' a launch," Ankit Panda, an adjunct senior fellow with the Federation of American Scientists, said on Twitter.
"The results of the recent important test will have an important effect on changing the strategic position of the DPRK once again in the near future," KCNA reported, using the initials of North Korea's official name, the Democratic People's Republic of Korea.
Tensions have risen ahead of a year-end deadline set by North Korea, which has called on the United States to change its policy of insisting on Pyongyang's unilateral denuclearization and demanded relief from punishing sanctions.
US President Donald Trump told reporters in June 2018 after his first summit with North Korean leader Kim Jong Un that North Korea had pledged to dismantle one of its missile installations, which US officials later identified as Sohae.
Commercial satellite imagery captured on Thursday by Planet Labs, showed new activity at the Sohae Satellite Launching Station and the presence of a large shipping container, CNN reported, with analysts suggesting it indicated a test was imminent.