According to a US monitor, North Korea’s main nuclear complex appeared to show continued activity on the site. In January and February, satellite images of the uranium enrichment facility showed specialised vehicles and equipment moving nearby the plant. But experts have said there is no clear sign of activity at the nuclear reactors. The US monitor website said: "In contrast to the reactor area of the complex, the UEP exhibited continual signs of operation throughout the winter months." They said the satellite images showed "uniquely configured, specialised railcars" arriving and departing the facility. South Korea’s Yonhap News Agency, reported that the images suggest the Uranium Enrichment Plant (UEP) has continued operations. Earlier this month, reports claimed that North Korea poses a new “catastrophic threat” to the world. Experts warned that the country’s nuclear weapons and ballistic missile testing could be the “biggest risk to the world” in 2021. The Council on Foreign Relations (CFR) explained the danger Kim Jong-un’s regime poses with its nuclear capabilities. In its annual preventative priorities survey, the CFR ranked a crisis stemming from North Korea’s continued development of nuclear weapons as the “top-ranked conflict concern for 2021”. During a meeting of the Worker’s Party of Korea last month, Mr Kim said the US was North Korea’s “foremost principal enemy”. He criticised America’s “hostile policy” towards the hermit kingdom.