North Korea may be preparing to launch a missile "within the next few days" after Japan detected radio signals, Kyodo News reported, citing government sources.
The sources, however, added that the signals may only be related to winter training for North Korea's military as satellite images have not shown a missile or a movable launch pad, Kyodo News said.
North Korea has not conducted a nuclear or missile test since Sept. 15, when it fired a ballistic missile that flew over the Hokkaido island and landed in the Pacific Ocean.
There has been speculation over what North Korean leader Kim Jong Un would do next after U.S. President Donald Trump put Pyongyang back on the state terror list on Nov. 20.
The Pentagon said it would continue to monitor Pyongyang's nuclear and ballistic missile activities "very closely" following the warning from Japan, said Yonhap News Agency.
