Kim Jong Un visits North Korean uranium enrichment facility in rare photos of his nuclear program

Experts say the photos suggest North Korea has dramatically increased its nuclear capabilities since it last invited foreign scientists to tour a centrifuge facility in Yongbyon in 2010.

“North Korea wants to send the message that it can dramatically expand its nuclear arsenal, and do it much faster than people thought,” said Lami Kim, a professor at the Daniel K. Inouye Asia-Pacific Center for Security Studies in Honolulu. “Whether they can build nuclear warheads is a big deal, but how many they can make now is also very significant,” Kim told NBC News.

“The purpose of releasing the images is to show North Korea's opponents their nuclear capabilities,” Kim added.

At the facility, the North Korean president praised scientists for their work in producing nuclear warheads and urged the development of a new type of centrifuge to “further solidify the foundation for the production of weapons-grade nuclear material.”

He also condemned the naval forces of the United States and its allies, which he described as a nuclear threat to North Korea.

The North Korean president has escalated his war rhetoric in recent months, declaring the United States and its treaty ally South Korea the main enemy while his country conducted tests of its nuclear-capable combat drones and missile launchers.

North Korea tested several ballistic missiles on Thursday, KCNA reported.

Officials in Seoul sharply criticized Pyongyang's nuclear plans.

“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 was quoted as saying by South Korea's Yonhap news agency.