This month, several American think-tanks and South Korean officials reported that satellite imagery showed potential preparations by North Korea.

"It's hasty to call it missile-related activity," Defence Minister Jeong Kyeong-doo told a parliamentary defence committee on Monday.

When asked if he could confirm whether North Korea's Sohae missile site was functionally restored, Jeong said it was inappropriate for intelligence authorities to comment on every media report one way or the other.

He also said there were signs of continued nuclear activity in North Korea, without elaborating.

Unification Minister Cho Myoung-gyon told a separate parliamentary panel that it was possible that the recent developments at the missile site were to bolster North Korea's leverage in negotiations.

"But given North Korea's continued work, thorough analysis is needed to find out its exact intentions," Cho said.

On Friday, North Korean Vice Foreign Minister Choe Son Hui told foreign diplomats and journalists in Pyongyang that leader Kim Jong Un was considering suspending talks with the United States and may rethink a freeze on missile and nuclear tests unless the United States made concessions.

The activity at Sohae appeared to begin shortly before US President Trump met Kim at a summit in Hanoi late last month.

The summit broke down over differences about US demands for North Korea to denuclearise and its demand for dramatic relief from international sanctions imposed for its nuclear and missile tests, which it pursued for years in defiance of UN Security Council resolutions.

Trump said after his first summit with Kim in Singapore last June that Kim had promised to dismantle the Sohae test site, a pledge the North Korean leader reiterated and expanded on at a summit with Moon in September.

Australian Associated Press