North Korean leader Kim Jong-un has visited a newly launched nuclear material production facility, vowing to "exponentially" strengthen the country's nuclear arsenal.

Axar.az reports, citing Yonhap, Kim made the visit the previous day, accompanied by key party officials, without disclosing the facility's location or other details.

Currently, North Korea is believed to house uranium enrichment facilities in three sites -- Yongbyon, Kangson and Kusong. It remains unclear whether the report suggests the existence of a fourth location.

Kim said the country's "weapons-grade nuclear material production capacity more than doubled" over the past five years, attributing the gains to the country's nuclear scientists, according to the report.

"Potential threats and unpredictable long-term crises further highlight the urgency" of expanding the nuclear deterrent "both in quality and quantity and in a sustained and accelerated way," Kim said, signaling that Pyongyang has no intention of stepping back from its nuclear ambitions.