REPUBLIKA.CO.ID, SEOUL -- North Korea may be planning a new missile test, South Korea's spy agency told lawmakers on Thursday, after brisk activity was spotted at its research facilities, just days before U.S. President Donald Trump visits Seoul.

Reclusive North Korea has carried out a series of nuclear and missile tests in defiance of U.N. Security Council resolutions, but has not launched any missiles since firing one over Japan on Sept. 15, the longest such lull this year.

However a flurry of activity including the movement of vehicles has been detected at the North's missile research facilities in Pyongyang, where the most recent missile test was conducted, pointing to another possible launch, South Korea's Intelligence Service said in a briefing to lawmakers.

It did not say how the activity was detected.