Satellite images from North Korea’s Punggye-ri site have suggested that the isolated country may be preparing for a nuclear test, The Guardian reported on Thursday. The United States-based monitoring group, 38 North, has said that North Korea looks “primed and ready” for what would be its sixth such test since 2006, the newspaper added.

If North Korea does go ahead with its nuclear test, it will be defying United States’ President Donald Trump’s threat of military action against the country. Trump earlier suggested that he would not hesitate to force North Korea to abandon its nuclear and ballistic missiles programme. Trump had previously referred to North Korea as a “menace” and had also said that he can solve the “problem” without China’s help.

“Commercial satellite imagery of North Korea’s Punggye-ri Nuclear Test Site from April 12 shows continued activity around the North Portal, new activity in the Main Administrative Area, and a few personnel around the site’s Command Center,” 38 North, a North Korea-related analysis website, said.

“In the courtyards of the main administrative area are approximately 11 probable tarp-covered pallets of equipment or supplies, a formation of personnel, and several individuals walking about,” the site added.

Tensions between the two countries spiked sharply on April 11 when the North Korean state media warned of a nuclear attack on the United States at any sign of American aggression. This occurred as a US Navy strike group steamed toward the western Pacific – a force Trump described as an “armada”.

On April 4, Pyongyang had fired a ballistic missile into the Sea of Japan, South Korea had said. The United States had also confirmed the development. The missile had been fired from North Korea’s eastern port of Sinpo and it reportedly flew around 60 km.