This was done publicly, in the presence of foreign journalists;
North Korea’s military blew up observation posts, security facilities and three test mines. Journalists from Great Britain, Russia, China, the United States and South Korea watched this. They reached the nuclear test site by train from Wonsan City, accompanied by North Korean military.
We climbed the mountain and watched the detonation from a distance of about 500 meters. There was a huge explosion that we felt under our feet. We flew dust and heat. It was very loud.
In late April, Kim Jong-un promised to close the largest nuclear test site in the DPRK to journalists. At least six nuclear tests of North Korea, the last in September 2017, took place at Pungery. In April 2018, Chinese scientists reported the collapse of the mountain on the test site, because of it fell into disrepair.