"(North Korea's) uranium enrichment facilities were known to be in normal operation even before the recent summit between the leaders of the United States and North Korea," Suh Hoon, the NIS chief, said in his recent address to lawmakers, as quoted by South Korean news agency Yonhap.
READ MORE: Study: Enough Uranium, Plutonium For 5-7 Nukes Made in North Korea Last Year
The outlet added that at the same closed briefing, the NIS chief said the agency had detected the movement of vehicles at North Korea's Saneum-dong missile research facility.
On Tuesday, several US think tanks and Yonhap reported that satellite pictures showed works were underway to restore the Sohae Satellite Launching Station at Tongchang-ri, which Kim also pledged to dismantle at his historic summit with US President Donald Trump in Singapore last year. Trump said he would be very disappointed in Kim if these reports turned out to be true.
Last September, North Korean leader Kim Jong Un and South Korean President Moon Jae-in said in a joint statement on the outcome of their third bilateral summit, that Pyongyang had promised to close its missile test range in Tongchang-ri and completely dismantle its nuclear facilities in Yongbyon.
The reports emerged days after the second Trump-Kim summit in Hanoi, which finished abruptly without any deal or declaration due to the parties’ failure to agree on the scale of North Korea’s denuclearization and US-led sanctions relief.