Apparent move seen as bid to set a positive tone ahead of talks with US President Donald Trump in June.
North Korea has carried out what it says is the demolition of its nuclear test site in the presence of foreign journalists.
The demolition happened on Thursday at the Punggye-ri site deep in the mountains of the North's sparsely populated northeast.
The dismantling of the nuclear test site was previously announced by North Korean leader Kim Jong-un ahead of his planned summit with US President Donald Trump next month.
The North's decision to close the site has generally been seen as a welcome gesture by 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 Trump's demands for denuclearisation.
The Korean Peninsula has seen a period of seemingly warming relations since an historic inter-Korea summit in April, when the two Koreas pledged to sign peace deal and pursue 'complete' denuclearisation.
The announcement comes shortly after North Korea threatened to walk away from the proposed summit with Trump, if Washington continues to do what it described as "unlawful and outrageous acts" that could damage Pyongyang's "goodwill".
North Korean Vice Foreign Minister Choe Son-hui said on Thursday that her country "will neither beg the US for dialogue, nor take the trouble to persuade them if they do not want to sit together with us", according to the Korean Central News Agency.
Trump has also expressed doubts as to whether the summit will go ahead. He told reporters that he will know by "next week" if the talks will proceed or not.
