South Korea's spy agency says usual levels of activity is under way at a missile base mentioned in a report by the Center for Strategic and International Studies(CSIS). 

The National Intelligence Service(NIS) unveiled the assessment in a briefing before the National Assembly’s Intelligence Committee on Wednesday. The agency said it was well aware of the Sakkanmol base which was among the 13 the CSIS termed as “undeclared” missile bases in its report released on Monday. 
  
The report described the base as being closest to the South Korean border and to be among the most actively maintained.

The NIS said Seoul and Washington are jointly assessing and sharing opinions on the latest issue and are closely observing the North’s missile and nuclear facilities and related activities. 

The spy agency is also said to have briefed the parliamentary committee on the status of the North’s missile arsenal.