Experts say the photos suggest North Korea has dramatically advanced its nuclear capabilities since the last time it invited foreign scientists to view a centrifuge facility, at Yongbyon in 2010.

“North Korea wants to send a message that it can expand its nuclear arsenal dramatically, 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 make nuclear warheads is already a big deal, but how many they can now make is also very significant,” Kim told NBC News.

The “purpose of releasing the pictures is to show their nuclear capabilities to North Korea’s adversaries,” Kim added.

At the facility, the North Korean leader praised scientists for their work in producing nuclear warheads, as he pushed for a new type of centrifuge to “further solidify the foundation for producing weapons-grade nuclear materials.”

He also blasted what he called anti-North Korea nuclear threats made by naval forces of the U.S. and its allies.

The North Korean leader has ramped up his war rhetoric in recent months, declaring U.S. and its treaty-ally South Korea as its prime enemy while his country conducted tests of its nuclear-capable attack drones and rocket launchers.

North Korea test fired multiple ballistic missiles on Thursday, KCNA said.

Officials in Seoul slammed Pyongyang for its nuclear developments.

“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 Ministry of Unification was quoted as saying by South Korea’s Yonhap news agency.