SEOUL, South Korea — North Korea said on Thursday that it had destroyed its only known nuclear test site, three weeks before its leader, Kim Jong-un, is scheduled to meet with President Trump.
North Korea allowed a select group of journalists from Britain, China, Russia, South Korea and the United States to watch its engineers destroy and close tunnels in its mountainous Punggye-ri test site, where the country has conducted all six of its nuclear tests. No independent outside nuclear monitors were invited to verify the dismantlement of the site.
The action came two days after Mr. Trump backed away from his demand that Mr. Kim completely abandon his nuclear arsenal without any reciprocal American concessions.
In the ceremony on Thursday, North Korea used explosives to destroy three of its four tunnels at the Punggye-ri test site, according to dispatches by reporters at the scene. The fourth tunnel had already been closed for fear of contamination after the North’s first nuclear test in 2006.
The North Koreans also blew up test-observation facilities, as well as barracks for site personnel and a metal foundry, the reports said. Two dozen international journalists were invited to witness explosives rigged inside the tunnels, and they were then escorted outside to viewing decks 500 yards away where they filmed the detonations.
North Korea invited mostly TV journalists to ensure that its action was broadcast worldwide.
Although some analysts feared the moves would be reversible, the reported demolition was the first concrete step North Korea has taken toward what Washington hopes will be a complete nuclear dismantlement under Mr. Kim.
It remained unclear whether the North destroyed all the tunnels on Thursday or had done so in a way that would allow the site to be used again. There were no independent expert monitors present to view the blasts and assess the extent of the destruction.
North Korea announced last month that it would end all nuclear and long-range ballistic missile tests as well as close the Punggye-ri test site. It said it no longer needed them because the country had completed a nuclear deterrent and wanted to focus on rebuilding its economy.
Mr. Kim announced the closure of the test site as he prepared for his planned June 12 summit meeting with Mr. Trump in Singapore. Mr. Trump called it “a very smart and gracious gesture!”
When he met the leaders of South Korea and China in recent weeks, Mr. Kim told them that he was willing to discuss relinquishing his country’s nuclear arsenal in return for security guarantees, the lifting of sanctions and other incentives from the United States.
But North Korea abruptly changed its tone last week, warning that Mr. Kim would not meet Mr. Trump if Washington insisted on its quick and “unilateral nuclear abandonment” without offering incentives. And earlier Thursday, North Korea warned it would call off the summit meeting with President Trump if American officials continued to make what the North considers threats against its leadership.
Despite doubts about North Korea’s intentions, analysts noted signs that the North has been preparing for the shutdown in Punggye-ri in recent weeks, taking down some buildings in a possible effort to remove sensitive information before the arrival of outsiders.
Some analysts have also played down the significance of North Korea’s decision to shut down the site. They said that after six tests, all conducted in deep tunnels, the site has most likely caved in and become too unstable for another test. Others cautioned that the North might be shutting the site down in a way that could allow it to be reopened quickly if negotiations with Washington sour.
In 2008, North Korea invited international journalists to watch it blow up a cooling tower of its nuclear reactor under a deal with Washington. But it restarted the reactor a few years later after negotiations over its nuclear program stalled.
But when he met with President Moon Jae-in of South Korea last month, Mr. Kim rebuffed skeptics of the Punggye-ri shutdown, saying that at the time that the site still had two functioning tunnels where nuclear tests could be conducted.
“It’s true that shutting down the Punggye-ri test site does not prevent North Korea from ever testing again,” said David Wright, senior scientist at the Union of Concerned Scientists. “If negotiations fail or situations change in the future, it could decide to tunnel at a different site and build the required infrastructure needed to test.”
But Mr. Wright called Thursday’s development “a meaningful and pretty dramatic action nonetheless.” It could take the North months or longer to reverse the disabling of the facilities at the site, he said.
North Korea said it had invited outside journalists to the dismantling ceremony to ensure transparency. But it waited until just a day before the event to let any South Korean journalists into the country.