Photos of North Korea's its uranium enrichment facility may show an undeclared site for building nuclear bombs just outside of its capital, analysts said.
North Korea for the first time showed images on Friday of the centrifuges that produce fuel for its nuclear bombs, as leader Kim Jong Un visited a uranium enrichment facility and called for more weapons-grade material to boost the arsenal.
The photos showed Kim walking between long rows of metal centrifuges, the machines that enrich uranium. The report did not mention the facility's location.
North Korea watchers and analysts said the site, known as Kangson, is suspected to be a covert uranium enrichment plant.
Jeffrey Lewis, a non-proliferation expert at the Middlebury Institute of International Studies, said five images of the inside facility, including of the "big" hall and an annex released by state media, match features of satellite imagery of the nuclear site.
The annex's odd shape and it unusual set of columns and beams are a "strong match" to the site North Korea constructed this year, he said.
"That's likely Kangson. It is an enrichment plant," Lewis added.
North Korea is believed to have several sites for enriching uranium.
Analysts say commercial satellite imagery has shown construction in recent years at the main Yongbyon Nuclear Scientific Research Center and the Kangson site, suggesting possible expansion in both places.
Colin Zwirko, a senior analytical correspondent with NK Pro, a Seoul-based website that monitors North Korea, said the photos and satellite imagery indicate the complex is Kangson.
In June, Rafael Grossi, the International Atomic Energy Agency's director general, said a new annex to the main building in the Kangson complex was being built this year, adding that the complex shared "infrastructure characteristics with the reported centrifuge enrichment facility at Yongbyon."
During the visit that was covered by North Korean media, Kim stressed the need to boost the number of centrifuges to "exponentially increase" the nuclear arsenal, and expand the use of a new type of centrifuge to strengthen the production of weapon-grade nuclear materials.
The photos that showed an advanced design of centrifuges and the hall with cascades connecting the centrifuges suggested the North Korea had made progress in uranium enrichment program, according to experts.
"The size of the cascades and hall shown also signify substantial capacity, perhaps not to the level of 'exponential growth' as Kim has mandated, but significant growth, nonetheless," 38 North, a Washington-based North Korea monitoring program, said in a note.
"It is probable that these centrifuges are North Korean designed and manufactured," it said, adding that the location showed in the photos could be Yongbyon.
The disclosure of its secretive nuclear facility could also be meant to influence the US election and send a message to the next administration that denuclearization is no longer possible, some experts said.
