"The DPRK's nuclear activities remain a cause for serious concern. The continuation of the DPRK's nuclear programme is a clear violation of relevant UN Security Council resolutions and is deeply regrettable," Grossi told the IAEA's board of governors, according to IAEA's website. DPRK refers to North Korea's official name, the Democratic People's Republic of Korea.
Plutonium is one of the two key ingredients to build nuclear weapons along with highly enriched uranium. The Yongbyon complex, north of the capital city of Pyongyang, has facilities to produce both ingredients. It's not clear exactly how much weapons-grade plutonium or highly enriched uranium has been produced at Yonbyong and where North Korea stores it.
Outside estimates on North Korea's nuclear arsenal vary. In 2018, a South Korean official told Parliament the North may have 20 bombs, to as many as 60.
US-led diplomacy aimed at persuading North Korea to abandon its nuclear programme in return for economic and political benefits has been deadlocked since a summit between President Donald Trump and Kim collapsed in early 2019. Trump rejected Kim's calls for extensive sanctions relief in return for dismantling the Yongbyon complex in what was seen as a limited denuclearisation step because North Korea had already built nuclear weapons and is believed to be running other covert bomb-making facilities.
In January, Kim vowed to enlarge nuclear arsenal and disclosed an array of high-tech weapons systems targeting the United States, saying the fate of bilateral ties depends on whether Washington withdraws its hostile policy on North Korea.
Some experts say Kim is attempting to pressure President Joe Biden's government to return to diplomacy and ease sanctions on the North.