North Korea is pressing on with its nuclear weapons program and several countries believe it has “probably developed miniaturised nuclear devices to fit into the warheads of its ballistic missiles,” according to a confidential UN report.

The report by an independent panel of experts monitoring UN sanctions said the countries, which it did not identify, believed North Korea’s past six nuclear tests had likely helped it develop miniaturised nuclear devices. Pyongyang has not conducted a nuclear test since September 2017.