International journalists left on a marathon journey to a North Korean nuclear test site on Wednesday, after Pyongyang belatedly cleared a number of South Korean media to witness what it says will be the dismantling of its only nuclear test facility.

Travel will involve an 11-hour train ride, a four-hour bus journey and then a hike of another hour, a reporter with Russia's RT said on Twitter.

North Korea has suspended talks with the South and threatened to pull out of an upcoming summit between North Korean leader Kim Jong Un and U.S. President Donald Trump, but the invitation to the media was seen as an indication that its unexpected offer to end its nuclear tests still held.