"The continuation of the DPRK's nuclear programme is a clear violation of relevant UN Security Council resolutions and is deeply regrettable," the International Atomic Energy Agency (IAEA) said in its report to members.

Among activities during the period since its last report in August 2019, the IAEA observed "indications consistent with the production of enriched uranium" at the reported Yongbyon nuclear site.

The Vienna-based agency noted in its report dated Tuesday that it had not had access to the Yongbyon site or other locations in North Korea, basing its analysis on "information available to it", including open source information and satellite imagery.

The US government, which claims that Pyongyang has pulled back on its nuclear ambitions, warned on Tuesday that the country continues to acquire materials and equipment for its ballistic missile program.

In a joint advisory the Treasury, Commerce and State Departments detailed North Korea's efforts to obtain everything from forestry trucks for missile launchers to common metals and materials that can be used in rockets, warning sellers to beware of sanctions on the country.

The advisory came as negotiations between the two countries aimed at halting North Korea's nuclear weapons progress, launched with fanfare at a 2018 summit between President Donald Trump and Kim Jong Un, have remained at a standstill since early last year.

Nevertheless, two months before a presidential election, Trump and his campaign have claimed success in dealing with North Korea with Secretary of State Mike Pompeo applauding the president for "lowering the temperature".