0356 GMT October 20, 2019
It marked the first official report of a weapons test by North Korea since it began a diplomatic process with Washington over its nuclear and missile program, AFP reported.
South Korea's Yonhap News Agency, quoting an unidentified government source, said the weapon could be a long-range cannon that the North has been developing for many years.
"Kim Jong-un... visited the test ground of the Academy of Defense Science and supervised a newly developed ultramodern tactical weapon test," said the official Korean Central News Agency.
It said the test was successful but did not specify the type of device involved.
Pyongyang's suspension of testing for atomic weapons and ballistic missiles has been key to this year's rapid diplomatic developments and North Korea-US negotiations, and has been repeatedly praised by US President Donald Trump.
Trump and Kim met at a historic summit in Singapore in June, where they signed a vaguely worded document on denuclearization of the peninsula.
Hours after the KCNA report, the US State Department said it was "confident" the process remained on track.
"At the Singapore Summit, President Trump and chairman Kim made a number of commitments regarding final, fully verified denuclearization and creating a brighter future for North Korea," a statement said.
"We are talking with the North Koreans about implementing all of those commitments. We remain confident that the promises made by President Trump and chairman Kim will be fulfilled."
Progress since Singapore has stalled as Washington and Pyongyang spar over the document's meaning. A return to testing would cast grave doubts over the future of the process.
But analysts all but ruled out the North having broken its promise to suspend nuclear or missile launches while negotiations are underway with the US.
There was no immediate indication any such test had been detected by the South.
"We don't see it as a military provocation of any significance", a Defense Ministry official told journalists without saying what the device was.
KCNA released only one photograph to accompany its report, showing uniformed men taking notes as Kim talked. The background gave few clues to what kind of weapon was involved.
Kim expressed "great satisfaction" and said the test marked a "decisive turn in bolstering the fighting capacity" of the North's military, KCNA said.