North Korea destroys nuclear test site near China border

SEOUL: Huge explosions reportedly shook North Korea´s only known nuclear test site on Thursday, in a ceremony that Pyongyang said had "completely" destroyed the facility near the Chinese border.

The Punggye-ri test site, located beneath a mountain in the far north east, hosted all six nuclear tests Pyongyang has conducted -- most recently last September. Earlier this month the North announced it would blow up the site´s access tunnels in front of invited foreign media.

The announcement came as the diplomatic push for Pyongyang to give up its nuclear weapons gathered pace with an unprecedented summit between North Korean leader Kim Jong Un and US President Donald Trump slated for June 12 in Singapore.

The site is located deep inside mountains in North Hamgyong province, which borders China. Surrounded by high, craggy peaks and carved deep into a granite mountain more than 2,000 metres high, the test site is said to be an ideal venue to withstand the huge forces unleashed by nuclear blasts.

The site´s location only became known in 2006 when the North conducted its first nuclear test under Kim´s late father Kim Jong Il. Activities have been closely watched through satellite imagery since then.

Tunnels can be seen entering the site from different directions. The first test was staged in the eastern tunnel, the second and third in the western tunnel and the remainder in the northern tunnel, according to intelligence authorities.

Yonhap reported three blasts in the tunnels Thursday followed by explosions that destroyed a barracks and other structures on the mountainside. Tests staged at the site have demonstrated the country´s rapid progress in its nuclear programme -- especially since Kim took power in 2011 and oversaw four atomic tests in only six years. The country´s first test was largely seen as a failure and produced an estimated yield of only about one kiloton, compared to as much as 250 kilotons in the sixth -- an explosion 16 times more powerful than the US atomic bomb dropped on Hiroshima in 1945.

But Punggye-ri´s proximity to China has become a source of concern for Beijing, as the tremor from the sixth test was felt across the border and prompted many residents to flee their homes in panic.

The growing impact of the blasts raised safety concerns, with some Chinese scientists warning that the site could pose a major radioactive threat to the wider region. A recent study by seismologists at the University of Science and Technology of China suggested rock had collapsed under the Mantap peak, making it unusable.

Kim himself has disputed those claims in conversations with his South Korean counterpart Moon Jae-In. "If they come and see, they will understand that there are two bigger tunnels than the existing test facilities and that they are in a very good condition," Kim said, according to comments released by the South.

A statement by North Korea´s Nuclear Weapons Institute on Thursday said prior to the blasts, reporters confirmed "two tunnels at the nuclear test ground were ready for use for carrying out very powerful underground nuclear tests at any time". Sceptics have said the move to destroy the site is an empty concession by Kim as the site is already suffering from "tired mountain syndrome" and may be obsolete. Others say North Korea has learned all it needs from the nuclear tests conducted there.