1053 GMT December 12, 2019
The comments follow a declaration by the North in 2013 vowing to restart all nuclear facilities, including the main nuclear reactor in Yongbyon that had been shuttered, Reuters reported.
"All the nuclear facilities in Yongbyon including the uranium enrichment plant and 5 MW graphite-moderated reactor were rearranged, changed or readjusted and they started normal operation," the state-run KCNA news agency said, quoting the director of its atomic agency.
"If the US and other hostile forces persistently seek their reckless hostile policy towards the DPRK and behave mischievously, the DPRK is fully ready to cope with them with nuclear weapons any time," the director was quoted as saying.
DPRK is the acronym for the North's official name, the Democratic People's Republic of Korea.
Innovations have been made to improve nuclear weapons "in quality and quantity as required by the prevailing situation," the director was quoted as saying.
Late on Monday, the North's space agency said it was readying a new satellite for launch, indicating it may fire an upgraded long-range ballistic missile timed to around the 70th anniversary of its ruling party on Oct.10.
North Korea is believed by experts to have enough fissile material to build 12 or more nuclear weapons, and is believed by US and South Korean officials to be working to miniaturize a nuclear warhead to mount on a delivery vehicle.
China said on Tuesday that it opposes nuclear weapons development on the Korean peninsula.
"We hope the relevant parties, under the current circumstances, can do more that is beneficial to safeguarding the peace and stability of the region and the peninsula," Foreign Ministry spokesman Hong Lei said in Beijing.
North Korea conducted three nuclear tests between 2006 and 2013.