North Korea has produced some 50 nuclear warheads and has enough fissile material for up to 90 warheads, a “significant” on-year increase from 2023, according to a new estimate from a Stockholm-based think tank.

The assessment in the Stockholm International Peace Research Institute’s (SIPRI) 2024 yearbook is up from its estimate of 30 assembled warheads last year and suggests Pyongyang continues to expand its nuclear arsenal despite international condemnation and U.N. sanctions.

“Like several other nuclear-armed states, North Korea is putting new emphasis on developing its arsenal of tactical nuclear weapons,” SIPRI researcher Matt Korda stated in a press release.