That has raised fears that North Korea may soon resume test launches of intercontinental ballistic missiles it had vowed to halt in April this year.

North Korea conducted several telemetry tests prior to some 40 missile test launches from 2016 to 2017. The tests are seen as precursors to ballistic missile launches and prompted monitoring by South Korea, the U.S. and Japan.

An intelligence source here said, "We have also detected the telemetry signals but have yet to detect any signs of an impending missile test."

However, the U.S. and the international community are growing increasingly concerned about North Korea's continued nuclear weapons and missile developments as dialogue remains deadlocked.