North Korea has carried out what it claims is the demolition of its only nuclear test site in the presence of foreign journalists.

The explosions deep in the mountains of the North's sparsely populated northeast were focused on three tunnels and a number of observation towers in the surrounding area.

The dismantling of the Punggye-ri nuclear site was announced by Kim Jong-un ahead of a planned summit with Donald Trump next month.

The demolition came as the North launched another verbal attack 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.

The North's decision to close the test site has generally been seen as a welcome gesture by Mr Kim to set a positive tone ahead of the summit. Even so, it is not an irreversible move and would need to be followed by many more significant measures to meet Mr Trump's demands for real denuclearisation.

By bringing in the foreign media, mainly television networks, the North is apparently hoping to have images of the closing broadcast around the world.

The North did not invite international inspectors to the ceremony, which limits its value as a serious concession.

Donald Trump reveals time and place for meeting with North Korea's Kim Jong Un

The outburst at Mr Pence, issued in the name of a top Foreign Ministry official, comes on the heels of another sharp rebuke of Mr Trump's newly appointed national security adviser, John Bolton, and has raised concerns that a major gap has opened between the two sides just weeks before the 12 June summit in Singapore.

In both cases, Pyongyang was trying to push back against hard-line comments suggesting North Korea may end up like Libya if it doesn't move forward quickly and irreversibly with concrete measures to get rid of its nuclear weapons.

Choe Son Hui, a vice minister of foreign affairs, was quoted by the North's state-run news agency slamming as "ignorant" and "stupid" comments Mr Pence made in an interview with Fox News that compared the nuclear-capable North to Libya. Libya gave up its program at an early stage only to see its longtime dictator overthrown and brutally killed years later.

North Korea: A road trip on the edge of the Chinese border Show all 20 1 /20 North Korea: A road trip on the edge of the Chinese border North Korea: A road trip on the edge of the Chinese border People have their picture taken with North Korea in the background, in Tumen, China. In the Chinese city of Dandong, signs of neighbouring North Korea are pervasive. REUTERS North Korea: A road trip on the edge of the Chinese border A North Korean woman is photographed from the Chinese side of the Yalu River near the town of Changbai, China as she walks between houses in the North Korean town of Hyesan. A week-long road trip along China's side of its border with North Korea revealed stark contrasts between China's bright towns and North Korea's dark villages. REUTERS North Korea: A road trip on the edge of the Chinese border North Korean souvenirs are displayed for sale on the banks of the Yalu River in Dandong in Liaoning province, China. In the Chinese city of Dandong, signs of neighbouring North Korea are pervasive. Reuters North Korea: A road trip on the edge of the Chinese border A large screen, which faces North Korea, broadcasts propaganda videos on an island on the Yalu River between North Korea and China, in the town of Linjiang in Jilin province, China. A week-long road trip along China's side of its border with North Korea revealed stark contrasts between China's bright towns and North Korea's dark villages. REUTERS North Korea: A road trip on the edge of the Chinese border A piece of clothing is used to make a gap in barbed wire near the closed bridge over the Yalu River on the Chinese side of the border with North Korea between towns of Ji'an and Linjiang, China. A week-long road trip along China's side of its border with North Korea showed places where it is porous. Reuters North Korea: A road trip on the edge of the Chinese border A tourist uses binoculars to look across to North Korea from a tower built on the Chinese side of the border between Russia (L), China (C) and North Korea (R) near the town of Hunchun in China. Reuters North Korea: A road trip on the edge of the Chinese border North Koreans are photographed from the Chinese side of the border as they stand next to the freezing Yalu River near the town of Linjiang, China. On a road trip along China's side of its border with North Korea, reporters found a group of North Koreans diving in the Yalu river who the Chinese locals said were searching for gold. REUTERS North Korea: A road trip on the edge of the Chinese border Women participate in a group dance exercise close to the Yalu River which runs between China and North Korea, in the town of Linjiang in Jilin province, China. A week-long road trip along China's side of its border with North Korea revealed stark contrasts between China's bright towns and North Korea's dark villages. REUTERS North Korea: A road trip on the edge of the Chinese border A sign reading, "Take the initiative to preserve order along the border," stands in a field at the border between China and North Korea just outside Dandong, Liaoning province, China. Reuters North Korea: A road trip on the edge of the Chinese border A couple prepare for a wedding photography session on a boat which takes tourists on sightseeing tours from the Chinese side of the Yalu River, close to the shores of North Korea, near Dandong, Liaoning province, China. In the Chinese city of Dandong, signs of neighbouring North Korea are pervasive. REUTERS North Korea: A road trip on the edge of the Chinese border Tourists travel on a boat taking them from the Chinese side of the Yalu River for sightseeing close to the shores of North Korea, near Dandong, Liaoning province, China. In the Chinese city of Dandong, signs of neighbouring North Korea are pervasive. REUTERS North Korea: A road trip on the edge of the Chinese border North Koreans are photographed from the Chinese side of the border as they stand next to the freezing Yalu River near the town of Linjiang, China. On a road trip along China's side of its border with North Korea, reporters found a group of North Koreans diving in the Yalu river who the Chinese locals said were searching for gold. REUTERS North Korea: A road trip on the edge of the Chinese border Women walk across a bridge from an island on the Yalu River, dividing North Korea and China, in the town of Linjiang in Jilin province, China. A week-long road trip along China's side of its border with North Korea revealed stark contrasts between China's bright towns and North Korea's dark villages. REUTERS North Korea: A road trip on the edge of the Chinese border A North Korean soldier and locals are photographed from the Chinese side of the border north of Dandong, China as they stand on the banks of the Yalu River, north of Sinuiju, North Korea. A week-long road trip along China's side of its border with North Korea revealed stark contrasts between China's bright towns and North Korea's dark villages. REUTERS North Korea: A road trip on the edge of the Chinese border North Korean girls are photographed from the Chinese side of the border as they collect water from the frozen Yalu River near Linjiang, China. A week-long road trip along China's side of its border with North Korea revealed stark contrasts between China's bright towns and North Korea's dark villages. REUTERS North Korea: A road trip on the edge of the Chinese border A man looks through binoculars towards North Korea on the Broken Bridge over the Yalu River that connects the North Korean town of Sinuiju and Dandong in Liaoning Province, China. In the Chinese city of Dandong, signs of neighbouring North Korea are pervasive. REUTERS North Korea: A road trip on the edge of the Chinese border North Koreans are photographed from the Chinese side of the border as they stand next to the freezing Yalu River near the town of Linjiang, China. On a road trip along China's side of its border with North Korea, reporters found a group of North Koreans diving in the Yalu river who the Chinese locals said were searching for gold. REUTERS North Korea: A road trip on the edge of the Chinese border North Korean fishermen are seen as a Chinese flag flutters from the Broken Bridge as the sun sets over the Yalu River between the North Korean town of Sinuiju and Dandong in Liaoning Province, China. In the Chinese city of Dandong, signs of neighbouring North Korea are pervasive. REUTERS North Korea: A road trip on the edge of the Chinese border North Koreans are photographed from the Chinese side of the border as they stand in the freezing Yalu River near the town of Linjiang, China. On a road trip along China's side of its border with North Korea, reporters found a group of North Koreans diving in the Yalu river who the Chinese locals said were searching for gold. REUTERS North Korea: A road trip on the edge of the Chinese border Women, photographed from the Chinese side of the border, are seen through binoculars fixed on a building on the Chinese side of the border for sightseers to look across to North Korea, as they cross the bridge from Namyang in North Korea towards the town of Tumen in China, Reuters

The summit plan has hit a number of speed bumps recently as both sides have begun trading barbs and taking tougher positions. Mr Trump met with South Korean president Moon Jae-in on Tuesday at the White House for consultations and suggested the summit could be delayed or even called off entirely.

Even so, both sides still seem to want to hold the meeting, which would be unprecedented.

Success in talks would be a huge accomplishment for Mr Trump. Meeting with the US president as an equal on the world stage would be a major coup for Mr Kim.