North Korea’s Punggye-ri nuclear test facility is shown in this DigitalGlobe satellite image in North Hamgyong Province, North Korea, May 23, 2018. (Digitalglobe/Reuters)

 North Korea said that it had destroyed its nuclear testing site Thursday afternoon, in a gesture designed to show it is still willing to embark on a diplomatic journey with the United States despite the recent ructions.

Foreign journalists taken to the Punggye-ri nuclear testing site said they had witnessed a “huge explosion” at the site, in the mountainous northeast of the country, and that the North Korean officials there told them the site had been dismantled.

The journalists from Russia, China, South Korea, Britain and the United States, reported watching the detonation from about 500 yards away.

“They counted it down — three, two, one,” said Tom Cheshire of Sky News, the 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.”

The Associated Press, Russia Today and China’s Xinhua also reported the closure from the site.

North Korea took the journalists to the site to report the event, but it did not allow in any experts, making it difficult to assess what, exactly, they had done.

President Trump on May 22 said a June summit in Singapore with North Korea could “happen later” if it doesn’t take place on June 12. 

Still, analysts said this was a move in the right direction, especially in light of threats from both Washington and Pyongyang to cancel a summit between President Trump and Kim Jong Un scheduled to be held in Singapore next month.

“This will be highly symbolic and a diplomatic first step,” said Frank Pabian, a former nuclear nonproliferation and satellite imagery expert at the Los Alamos National Laboratory. “But in and of itself, it won’t change anything about North Korea’s nuclear capabilities.”

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

Following a historic summit with South Korean President Moon Jae-in at the end of last month, Kim agreed to embark on a number of steps to show he was serious about dealing with the United States, the North’s avowed enemy.

This included a plan to work toward “the complete denuclearization of the Korean Peninsula” — a phrase that Trump took to mean Kim wanted to give up his weapons, while most analysts said it was code for a drawn-out process under which both sides would have to make concessions.

South Korean President Moon Jae-in met with North Korean leader Kim Jong Un on April 27. Here are key moments from the historic talks. 

As the wrangling over the definition of “denuclearization” continues, both Trump and a senior aide to Kim have raised the prospect of canceling the summit, scheduled for June 12. The North Korean regime has particularly balked at the Trump administration’s repeated references to Libya, which gave up its nuclear weapons in return for sanctions relief. The Libyan leader, Moammar Gaddafi, was overthrown and brutally killed a few years later.

Still, North Korea proceeded with its pledge to dismantle the site where all six of its nuclear tests took place.

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 Wednesday.

They left Wonsan, on North Korea’s east coast, at about 6 p.m. local time, for a 300-mile journey that the reporters said would involve a 12-hour train ride then four hours on a bus, followed by an hour or two hiking through the mountains.

Satellite images showed observation platforms had been set up at the portals to the site, as well as at the command center and main administration area.

About 26 hours after their departures, the journalists sent word of the explosion, but they will have no means of sending images until they make the return journey to Wonsan, likely arriving some time Friday.

Restrictions on them were tight, with the Russia Today journalist reporting on the way to the site that the window blinds on the train were secured closed so they couldn’t see out. They were, however, served a 10-course banquet on the train.

The journalists’ gear was closely checked, with Sky News’s Cheshire reporting that dosimeters were confiscated so they couldn’t measure how much, if any, radiation was leaking from the site.

The nuclear test site is about 10 miles north of the village of Punggye-ri and consists of a series of tunnels under the mountains, entered through four portals.

The east portal, through which North Korea conducted its first nuclear test, in 2006, has been abandoned for more than a decade and is no longer accessible by road.

The following five tests all took place through the north portal. The last, conducted in September, was widely considered to have been a hydrogen explosion. It caused a 6.3-magnitude earthquake at the site and had a yield of as much as 250 kilotons. In comparison, the American nuclear bomb detonated over Hiroshima in 1945 had a yield of about 15 kilotons of energy.

Since that test, there have been suggestions that Mount Mantap might be suffering from “tired mountain syndrome,” and many experts say that the north portal tunnels are now unusable.

However, the west and south portals have never been used and were still considered viable for future tests.

North Korea’s Foreign Ministry announced 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 and guard posts.

“In parallel with dismantlement of the nuclear test ground, guards and researchers will be withdrawn and the surrounding area of the test ground be completely closed,” the ministry said in a statement.

Satellite images had shown buildings around the portals coming down in the lead-up to the site’s closure.

Although no nuclear experts were allowed to attend the event, Pabian, who now writes for the specialist website 38 North, said that officials from organizations like the Comprehensive Test Ban Treaty Organization would still be able to carry out testing if they were ever granted access to the site.

The verdict is still out on whether North Korea is seriously prepared to discuss denuclearization with the United States, with many analysts doubting Kim would give up the weapons he considers vital to his legitimacy and for fending off external threats.

 After Thursday’s outburst, in which Pyongyang called Vice President Pence “a political dummy” for comparing North Korea to Libya, analysts took to Twitter with sarcastic remarks underlining how far apart the countries remain.

“Yep. North Korea is definitely ready to give up its nukes,” James Acton of the Carnegie Endowment for International Peace wrote tongue-in-cheek.

But one thing would become clear if North Korea dismantles the Punggye-ri site Thursday: it has finished with its nuclear testing.

North Korean state media called last September’s nuclear test a “perfect success” and said it had attained its “final goal of completing the state nuclear force” — a signal that it had done all the tests it needed to.

Then, last month as the inter-Korean summit approached, Kim said at a Workers’ Party meeting in Pyongyang that no further tests would be needed because the nuclear and missile programs were completed.

“The mission of the northern nuclear test ground has thus come to an end,” Kim told his top cadres, according to a state media report.

By acquiring this “powerful treasured sword for defending peace,” North Koreans could now “enjoy the most dignified and happiest life in the world,” he said.