SEOUL, June 4 (Reuters) - North Korean leader Kim Jong Un visited a newly operational nuclear ‌material production facility and called for an "exponential" ‌expansion of the country's atomic arsenal, state media KCNA said on ​Thursday.

Kim said production capacity for weapons-grade nuclear material had reached more than double its previous level over the past five years and instructed officials to further ‌increase output to ⁠meet long-term strategic goals.

During the visit, Kim was briefed on new production processes incorporating ⁠more advanced technology and reviewed current output targets and future plans, KCNA reported.

Kim said the expansion was ​necessary given ​what he called worsening ​security threats and long-term ‌confrontation with hostile forces, and reaffirmed the country’s policy of continuously increasing its nuclear deterrent.

KCNA said a key consultative meeting on bolstering nuclear forces was held the same day, at which Kim outlined guidelines ‌for accelerating both the qualitative ​and quantitative expansion of North ​Korea’s nuclear arsenal.

Kim ​said the country had made “responsible and ‌significant decisions,” including setting out ​the sequence and ​safeguards for executing what he described as a vast plan to strengthen nuclear forces “exponentially.”

North Korea ​had “set a transformative ‌milestone for the advancement of nuclear capabilities,” ​he said.

(Reporting by Kyu-seok Shim; Editing by Chris ​Reese and Nia Williams)