TOKYO • Reporters at North Korea's Punggye-ri nuclear test site when it was reportedly being destroyed described a series of explosions throughout the day, three of them in entry tunnels to the underground facility, followed by explosions that demolished a nearby barracks and other structures.

Dozens of journalists from Russia, China, South Korea, Britain and the United States reported watching the detonation from about 500m away yesterday.

"They counted it down - three, two, one," said Mr Tom Cheshire of Sky News, a British broadcaster.

"There was a huge explosion; you could feel it. Dust came at you; the heat came at you. It was extremely loud. It blew an observation tower to complete smithereens."

As North Korea did not allow any experts into the site, it was difficult to assess what exactly Pyongyang had done. Still, analysts said this was a move in the right direction, despite US President Donald Trump cancelling a planned summit in Singapore on June 12 after a war of words with Pyongyang.

The high-stakes talks were aimed at ridding the reclusive state of its newly acquired nuclear weapons and improving US-North Korea ties.

"This will be highly symbolic and a diplomatic first step," Mr Frank Pabian, a former nuclear non-proliferation and satellite imagery expert at the Los Alamos National Laboratory, said about the reported dismantling of the Punggye-ri site.

"But in and of itself, it won't change anything about North Korea's nuclear capabilities."

North Korea has signalled that it no longer needs to test its nuclear devices because it has mastered the technology, a claim that is not without credibility.

State news agency KCNA said yesterday that the dismantling of the nuclear test ground completely closed the tunnel entrances, adding that two tunnels there had been ready for use in "powerful underground nuclear tests".

There was no leakage of radioactive material or adverse impact on the surrounding environment from the dismantling, KCNA added.

"The discontinuance of the nuclear test is an important process moving towards global nuclear disarmament," the news agency said.

A total of 30 journalists, all of them from television outlets except for four South Korean print reporters, were taken to the test site overnight on Wednesday. Their gear was closely checked, with Sky News reporting that dosimeters were confiscated so that they could not measure how much, if any, radiation was leaking from the site.

North Korea's Foreign Ministry announced on May 12 that it would close the site by collapsing all of the tunnels through explosions, then completely blocking the portals and removing all surrounding buildings, including research institutes.

WASHINGTON POST, AGENCE FRANCE-PRESSE, REUTERS