Photos and infrared imaging indicate vehicles moving in and out of the facility at Sanumdong

North Korea has pressed ahead with construction at the factory that produced the country’s first intercontinental ballistic missiles capable of reaching the US, despite ongoing negotiations over the fate of its nuclear and missile programmes.

US spy satellites captured photos and infrared images that indicate vehicles moving in and out of the facility at Sanumdong, but do not show how advanced any missile construction might be, a US official told Reuters.

South Korea to investigate North Korean women's 'mass defection' Read more

The Washington Post reported on Monday that North Korea appeared to be building one or two new liquid-fuelled intercontinental ballistic missiles at the large research facility on the outskirts of Pyongyang, citing unidentified officials familiar with intelligence reporting.

According to the anonymous US official who spoke to Reuters, one photo showed a truck and covered trailer similar to those the North has used to move its ICBMs. As the trailer was covered, it was not possible to know what, if anything, it was carrying.

The White House said it did not comment on intelligence.

The evidence obtained this month is the latest to suggest ongoing activity at North Korea’s nuclear and missile facilities despite talks with the US and a June summit between North Korean leader, Kim Jong-un, and Donald Trump.

Mintaro Oba, a former US diplomat who worked on North Korea policy, said: “It reflects an important fact: despite what US officials have been saying, North Korea didn’t commit to much of anything on denuclearisation.

“It’s not surprising that North Korea would want to proceed with elements of their nuclear and missile programmes until a real deal is reached. They’re not just going to stop because we had a summit.”

Trump declared soon after the Kim meeting that North Korea no longer posed a nuclear threat. Kim committed in a broad summit statement to work towards denuclearisation, but Pyongyang has offered no details as to how it might go about that, and subsequent talks have not gone smoothly.

North Korean officials are considering disposing of a limited number of nuclear warheads in a deal with the US while secretly maintaining a nuclear arsenal, according to US intelligence reported by the Washington Post.

North Korea hands over remains of US soldiers killed in Korean war Read more

It is not the first time US intelligence has clashed with the president’s optimism. In late June, US officials told US media outlets that intelligence agencies believed North Korea had increased production of fuel for nuclear weapons, and that it did not intend to fully give up its nuclear arsenal. Weeks after the summit, commercial satellite images showed the North was upgrading its only known nuclear power plant, the source of fuel for its weapons programme.

The US secretary of state, Mike Pompeo, told the Senate foreign relations committee last week that North Korea was continuing to produce fuel for nuclear bombs despite its pledge to denuclearise. But he insisted the Trump administration was still making progress in its talks with Pyongyang.

Joel Wit, a former state department negotiator and founder of 38 North, a North Korea monitoring project, said it was unrealistic to expect North Korea to stop its programmes “until the ink is dry on an agreement.“

That was the case with US negotiations with the Soviet Union during the cold war, and more recently with Iran, “which continued to build more centrifuges capable of producing nuclear material even as it negotiated with the United States to limit those capabilities,” Wit said.

News of the construction came as generals from North and South Korea met at the border village of Panmunjom inside the demilitarised zone – the second such meeting since the leaders of the two countries held a summit in April about reducing military tensions.

Experts have said the talks could lead to a reduction in military presence along the border, but there are doubts about the progress that can be made without a similar breakthrough on the nuclear issue.

The Sanumdong factory produced two Hwasong-15 ICBMs, North Korea’s longest-range missiles, but the US official noted that Pyongyang still had not tested a reliable re-entry vehicle capable of surviving a high-velocity trip through the Earth’s atmosphere and delivering a nuclear warhead.

The official said it was possible that any new missiles the North was building may be for further testing of such vehicles and of more accurate guidance systems.

“They seem to have figured out the engines, but not all the higher-tech stuff, and that might be what this is about,” the official said.