June 14 (UPI) -- North Korea continues to develop weapons of mass destruction and the regime is believed to have increased its nuclear arsenal, according to a Swedish think tank.
The Stockholm International Peace Research Institute said in an annual report published Monday that Pyongyang is one of nine nuclear-armed states in the world -- a group that includes the United States Russia, Pakistan and Israel.
North Korea has stayed away from nuclear weapons tests since 2017 and did not test-launch long-range ballistic missiles in 2020, the report said.
But the regime "continued production of fissile material and development of short and long-range ballistic missiles" away from the public eye, the institute said.
The think tank estimates that Pyongyang currently has in possession anywhere from 40 to 50 nuclear weapons, up from last year, when the country was believed to have stockpiled 30 to 40 warheads.
It said its estimates are based on the number of warheads that North Korea could "potentially build" with the fissile material available.
"There is no publicly available evidence that North Korea has produced an operational nuclear warhead for delivery by an intercontinental-range ballistic missile," the institute said.
"But it might have a small number of warheads for medium-range ballistic missiles."
The report said that the figures for North Korea are "highly uncertain" and are not included in its final tally of 13,080 weapons globally.
The advisory comes a week after International Atomic Energy Agency Director General Rafael Grossi said a suspected uranium enrichment site in North Korea appears to be active.
Analysts previously have said the Kangson facility in Chollima-guyok, outside Pyongyang, is designed to produce Uranium-235, which can go toward manufacturing nuclear weapons.
Grossi also said that there are no indications of activity at the 5-megawatt nuclear reactor in Yongbyon.