According to the Yomiuri Shimbun newspaper's sources, North Korea tested radio wave detectors that are installed in ballistic missiles to allow the military to track the missiles' speed, location and trajectory, the outlet reported, noting that such tests had often preceded Pyongyang's ICBM launches.
Pyongyang has yet to comment on the media reports.
In late April, North Korean leader Kim Jong-un announced that the country would suspend its ICBM launches and missile tests ahead of the summits with South Korean President Moon Jae-in and US President Donald Trump.
In addition to this, during September's inter-Korean summit, North Korea pledged to close its missile test range in Tongchang-ri and completely disassemble nuclear facilities in Yongbyon.
Pyongyang conducted its latest missile launch in November last year.