Asked to elaborate on the punishment, the lawmaker said that the NIS is still trying to figure it out.

The bureau is seen as an influential military institution as it leads the crucial personnel management of other military bodies such as the Ministry of People's Armed Forces. It was once headed by Choe. 

The punishment against Hwang came as a surprise as he had been seen as one of the most powerful military figures.

Hwang rose to prominence in 2014 as he took the helm of the bureau. He replaced Choe, sparking speculation that North Korean leader Kim Jong-un might be pitting them against each other to keep them in check and ensure their loyalty. 

The NIS also reported that the North has been focusing on forestalling a possible negative impact of the tightening international sanctions on public sentiment. The isolated state has been under crippling sanctions due to its provocations, including its sixth and most powerful nuke test on Sept. 3.

"(Pyongyang) has devised a system whereby party organs report people's economic hardships on a daily basis, and it has banned any gatherings related to drinking, singing and other entertainment and is strengthening control of outside information," the NIS said.

The spy agency, in addition, said that it has been closely watching the possibility of a new missile test by the North this year to escalate its threat to the United States under the disguise of peaceful space development.

As to the possibility of another nuclear experiment, the NIS said there has not been any sign of an imminent test.

"But we forecast that depending upon North Korean leader Kim's determination, a nuclear test is possible any time," the agency said.

It, moreover, said that Tunnel 3 of the North's Punggye-ri test site is available for a test, while the North has recently resumed construction on Tunnel 4 with Tunnel 2 left unattended. (Yonhap)