North Korea was reportedly continuing its nuclear and missile activity even after the summit between President Donald Trump and the former nation’s leader Kim Jong Un in June saw the latter agreeing to permanently close its nuclear program, South Korea's spy agency, the National Intelligence Service (NIS), was quoted as saying Wednesday. 

Participants said the agency made this statement in a report during a closed-door meeting of the parliamentary intelligence committee held Wednesday. The report was a result of the very little progress the denuclearization process has made in recent weeks, which included the cancellation of the planned high-level talks between Washington and Pyongyang last week.

"Nuclear and missile-related activity is believed to be going on even after the North-U.S. summit. It is presumed that activities like nuclear development and nuclear warhead miniaturization are still going on,” a senior official of the agency was quoted as saying during the meeting, Yonhap News reported.

The agency also stated the nation was showing same levels of activity at a missile base that was alleged to be North Korea's hidden, "undeclared" missile site.

Earlier this week, a group at the Center for Strategic and International Studies called Beyond Parallel said they had located 13 out of an estimated 20 undeclared missile operating bases including one in the Sakkanmol region.

“The dispersed deployment of these bases and distinctive tactics employed by ballistic missile units are combined with decades of extensive camouflage, concealment and deception practices to maximize the survival of its missile units from pre-emptive strikes and during wartime operations," Beyond Parallel's report said, adding, “Sakkanmol currently houses a unit equipped with SRBMs but could easily accommodate more capable medium-range ballistic missiles (MRBMs)."

Seoul, however, rejected these allegations by stating it was aware of the Sakkanmol base. Trump also said the report was false as United States too knew about the base.

According to the NIS, the activities at the Sakkanmol missile base were as usual.

"We are closely monitoring North Korea's other missile sites. Seoul and Washington are sharing information about North Korea's missiles and closely watching its nuclear and missile facilities and activities,” the agency said.

Kim Trump North Korea's leader Kim Jong Un shakes hands with President Donald Trump at the start of their historic summit at the Capella Hotel on Sentosa island, Singapore, June 12, 2018. Photo: SAUL LOEB/AFP/Getty Images

Last Wednesday, the meeting between U.S. Secretary of State Mike Pompeo and his North Korean counterpart, scheduled to take place in New York, was postponed to a later date.

"We will reconvene when our respective schedules permit. Ongoing conversations continue to take place. The United States remains focused on fulfilling the commitments agreed to by President Trump and Chairman Kim at the Singapore Summit in June,” U.S. State Department spokeswoman Heather Nauert said without specifying a reason for the last minute cancellation.

Last month, reports stated North Korea was preparing several of its nuclear and missile test sites for international inspections.

"Signs have been detected that North Korea is doing some preparations and intelligence-related activity over a possible visit by outside experts, as it shut down the nuclear test site and demolished some of the missile launching facilities at Dongchang-ri," Kim Min-ki of the ruling Democratic Party quoted NIS as saying.