WASHINGTON (AP) — U.S. intelligence officials say North Korea's nuclear test yielded an explosion of "approximately several kilotons."

In a statement Tuesday, the Office of the Director of National Intelligence said North Korea "probably conducted an underground nuclear explosion in the vicinity of P'unggye." It said the explosion yield was "approximately several kilotons" and that analysis of the event is continuing.

South Korea's Defense Ministry said it detected an estimated explosive yield of 6-7 kilotons.

President Barack Obama called North Korea's action "highly provocative" and said it threatens U.S. security and international peace.