In this Thursday, May 24, 2018 photo, smoke rises from North Korea's nuclear test site after an explosion in Punggye-ri, North Korea. North Korean leader Kim Jong Un made good on his promise to demolish his country's nuclear test site, which was formally closed in a series of huge explosions Thursday as a group of foreign journalists looked on. (Korea Pool/Yonhap via AP)

PUNGGYE-RI, North Korea (AP) — North Korean leader Kim Jong Un made good on his promise to demolish his country’s nuclear test site, which was formally closed in a series of huge explosions Thursday as a small group of foreign journalists watched.

The explosions at the test site deep in the mountains of the North’s sparsely populated northeast were supposed to build confidence ahead of a planned summit next month between Kim and President Donald Trump.

But Trump canceled the meeting on Thursday, citing “tremendous anger and open hostility” in a North Korean statement released earlier in the day.

The blasts were centered on three tunnels at the underground site and a number of buildings in the surrounding area.

North Korea held a closing ceremony afterward with officials from its nuclear arms program in attendance.

The group of journalists that witnessed the demolition, which touched off landslides near the tunnel entrances and sent up clouds of smoke and dust, included an Associated Press Television crew.

North Korea’s state media called the closure of the site part of a process to build “a nuclear-free, peaceful world” and “global nuclear disarmament.”

“The dismantling of the nuclear test ground conducted with high-level transparency has clearly attested once again to the proactive and peace-loving efforts of the DPRK government being made for assuring peace and stability on the Korean Peninsula and over the world,” the North’s official news agency reported late Thursday.

North Korea’s formal name is the Democratic People’s Republic of Korea.

Kim announced his plan to close the site, where North Korea has conducted all six of its underground nuclear tests, ahead of a summit with South Korea’s President Moon Jae-in in April and the planned summit with Trump next month.

But even as North Korea made good on its gesture of detente, it lobbed a verbal salvo at Washington, calling Vice President Mike Pence a “political dummy” and saying it is just as ready to meet in a nuclear confrontation as at the negotiating table.

Trump responded by canceling the summit, saying in a letter to Kim, “Sadly, based on the tremendous anger and open hostility displayed in your most recent statement, I feel it is inappropriate, at this time, to have this long-planned meeting.”

North Korea’s decision to close the Punggye-ri nuclear test site had generally been seen as a welcome gesture by Kim to set a positive tone ahead of the summit.

In a statement earlier Thursday, South Korea’s National Security Council called the closing the North’s “first measure toward complete denuclearization.”

Not everyone was as optimistic, however.

The closing of the site is not an irreversible move and would need to be followed by many more significant measures to meet Trump’s demand for real denuclearization.