North Korea has for the first time offered a glimpse into a uranium enrichment facility which produces material for its nuclear weapons.

Photographs showed its leader Kim Jong Un, who had earlier vowed to “exponentially” increase the country’s stash of nuclear weapons, inspecting the area.

The state’s Korean Central News Agency (KCNA) said in a report on Friday that he had similarly called for the uranium facility to increase its production.

Enriched uranium is essential in the manufacturing of nuclear warheads.

The photograph shows Mr Kim walking past rows of centrifuges and talking to military officials. Their publication comes amid heightened tensions on the Korean peninsula.

“[Mr Kim] went round the control room of the uranium enrichment base to learn about the overall operation of the production lines,” KCNA reported, adding that he “felt strong” to see the site.

The South Korean government has said it strongly condemns the North’s plans to increase production.

North Korea did not reveal when Mr Kim made the visit, nor which facility he visited – whether this is part of its sprawling Yongbyon nuclear complex, or another undisclosed site. Experts have long suspected that North Korea is covertly running at least one uranium enrichment facility, in addition to its well-known Yongbyon site.

Leif-Eric Easley, a professor at Ewha University in Seoul said North Korea has disclosed the facility to “boast of its nuclear development and signal that its weapons program is irreversible”.

“The Kim regime may also be flaunting that it still enjoys diplomatic and economic support from Russia and China, despite its nuclear buildup,” Prof Easley told the BBC.

Hong Min, a senior analyst at the Korea Institute for National Unification, had told news agency AFP that the photographs could be a “message” to the upcoming US presidential election, meant to show the next administration that it would be “impossible to denuclearise North Korea”.

“It is also a message demanding other countries to acknowledge North Korea as a nuclear state,” Mr Hong said.

South Korea’s Ministry of Unification has condemned the North for publicising the facility, adding that the illegal deployment of nuclear weapons violates several resolutions set by the UN Security Council.

“Any nuclear threat or provocation by North Korea will be met with an overwhelming and strong response from our government and military, based on the solid extended deterrence of the South Korea-US alliance,” the unification ministry said.

It is not known how many nuclear weapons North Korea has, but one recent estimate puts the number at 50, with sufficient material to produce another 40.