South Koreans watch a TV report on North Korea's missile launch on September 16, 2017. (Photo: AP)

The Donga Ilbo daily, quoting a government source, said satellite pictures showed ballistic missiles mounted on launchers being transported out of hangars in the North Phyongan Province near Pyongyang. US military officials believe the movement could indicate preparation for a test launch of a missile comparable to the Hwasong-14 inter-continental ballistic missile which is capable of reaching Alaska or Hwasong-12 intermediate-range ballistic missile that Pyongyang recently threatened to fire towards the US territory of Guam. Another probability could be the testing of the new Hwasong-13 inter-continental ballistic missile that targets the US’s west coast.

A South Korean defence spokesman refused to comment on the report, saying it is keeping a close watch over the North.