SEOUL, South Korea — North Korea for the first time showed images of the centrifuges that produce fuel for its nuclear bombs on Friday, as leader Kim Jong Un visited a uranium enrichment facility and called for more weapons-grade material to increase the arsenal.

The state media report on Kim’s visit to the Nuclear Weapons Institute and a production base for weapons-grade nuclear materials was accompanied by the first photos of the centrifuges, providing a rare look inside North Korea’s…