A shallow earthquake which hit North Korea near the country's nuclear test site Saturday was likely a seismic aftershock, nuclear test ban watchdog CTBTO said.

"The most probable hypothesis currently is that it is the consequence of the previous event ... which could still have further repercussions," Lassina Zerbo, head of the Comprehensive Nuclear Test Ban Treaty Organisation (CTBTO) told AFP, referring to Pyongyang's September 3 nuclear test which sparked international outrage.