It is premature to say whether recent activity at some of North Korea's rocket facilities involved preparation for a missile launch, South Korea's defense minister told a parliamentary hearing Monday.

Early in March, several American think tanks and South Korean officials reported that satellite imagery showed possible preparations for a launch from the Sohae rocket launch site at Tongchang-ri, North Korea, which has been used in the past to launch satellites but not intercontinental ballistic missiles capable of delivering a nuclear warhead.

"It's hasty to call it missile-related activity," Defense Minister Jeong Kyeong-doo told a parliamentary defense committee.