North Korea appears to have blown up tunnels at its only nuclear test site, in a move to reduce regional tensions.
Foreign reporters at the Punggye-ri site in the north-east said they witnessed a huge blast. Pyongyang later said the site had been dismantled.
The move by the North is seen as part of a diplomatic rapprochement with South Korea and the US.
But scientists believe it partially collapsed after the last test in September 2017, rendering it unusable.
Independent inspectors were not allowed to witness the process of the dismantling of the Punggye-ri site in the mountainous region of the country, and some worry it could be easily reversible, reports the BBC.
It comes ahead of a planned summit between US President Donald Trump and North Korean leader Kim Jong-un in Singapore on June 12.
However, in recent days both countries have said the meeting could be delayed or even called off, amid sharp verbal exchanges between US and North Korean officials.
Three tunnels were collapsed in a series of explosions in front of about 20 handpicked international journalists.
Two blasts were reportedly carried out in the morning, and four in the afternoon.
Tom Cheshire of Sky News was among the journalists present. He said the doors to the tunnels were "theatrically rigged" with "wires everywhere".
North Korea's Nuclear Weapons Institute later said in a statement that the dismantling of the site "was done in such a way as to make all the tunnels of the test ground collapse by explosion and completely close the tunnel entrances", NK News website says.
North Korea has conducted six nuclear tests since 2006 in a system of tunnels dug below Mount Mantap.
It is thought to have been the North's main nuclear facility and until now the only active nuclear testing site in the world.
It is located about 370km (230 miles) north-east of Pyongyang.
Earlier on Thursday, North Korean official Choe Son-hui dismissed remarks by US Vice-President Mike Pence as "stupid", casting further uncertainty over the planned 12 June summit.
Choe, who has been involved in several diplomatic interactions with the US over the past decade, said he North would not "beg" for dialogue and warned of a "nuclear showdown" if diplomacy failed.
His comments came after Pence warned that North Korea "may end like Libya" - where then-leader Muammar Gaddafi was killed by rebels in 2011 after renouncing nuclear weapons eight years earlier.
BDST: 1940 HRS, MAY 24, 2018
AP
