North Korea is showing a "very serious increase" in its ability to produce atomic weapons, the head of the UN nuclear watchdog said Wednesday on a visit to Seoul.
The diplomatically isolated north is believed to operate multiple facilities for enriching uranium, a key step in making nuclear warheads, South Korea's spy agency has said.
They include one at the Yongbyon nuclear site, which Pyongyang purportedly decommissioned after talks but later reactivated in 2021.
"In our periodic assessments, we have been able to confirm that there's a rapid increase in the operations" of the Yongbyon reactor, International Atomic Energy Agency (IAEA) chief Rafael Grossi told reporters in Seoul.
The agency also observed a rise in operations at Yongbyon's reprocessing unit and light-water reactor, as well as the activation of other facilities, Grossi said.
"All that points to a very serious increase in the capabilities of (the) DPRK in the area of nuclear weapons production, which is estimated at a few dozen warheads," he said, using North Korea's official name.
North Korea, which conducted its first nuclear test in 2006, is under rafts of UN sanctions for its banned weapons programs.
It has declared that it will never surrender its nuclear weapons, and cut off access to IAEA inspectors in 2009.
The agency has noted the construction of a "new facility similar to the enrichment facility in Yongbyon", Grossi said.
It was "not easy to calculate" any production increases without visiting the site.
However, "we consider, looking at external features of the facility, that there will be significant increase in the enrichment capacity of the DPRK", he said.
Asked whether Russia was assisting North Korea's nuclear development, Grossi said the IAEA had not seen "anything in particular in that regard".
North Korea has sent ground troops and artillery shells to support Russia's invasion of Ukraine, and observers say Pyongyang is receiving military technology assistance from Moscow in return.
