North Korea made preparations to conduct a nuclear test during the first six months of this year, according to excerpts from a secret United Nations report.

According to Reuters, independent UN monitors reported that "work at the (Punggye-ri) nuclear test site paves the way for additional tests to develop nuclear weapons."

The monitors wrote that "North Korea has continued to develop its capability to produce fissile material at the Yongbyon site."

Yongbyon is North Korea's main nuclear facility, operating its first nuclear reactors.

The United States has long warned that North Korea is preparing to conduct a seventh nuclear test, vowing to impose further sanctions on Pyongyang.

The monitors also explained that investigations showed that Pyongyang is responsible for stealing cryptocurrencies worth hundreds of millions of dollars in a single major hack to fund its nuclear and missile programs.