The intelligence body said although North Korea remains silent over the death, a growing number of high-ranking and overseas officials are becoming aware of the news.

The spy agency also provided lawmakers with various updates on developments taking place in Pyongyang.

The NIS said North Korea is prepared to conduct nuclear tests at anytime, claiming such facilities are well managed even during the winter season. It said the No. 2 tunnel at the North's nuclear test site in Punggye-ri has been maintained throughout the winter, and that the No. 3 tunnel can be used to conduct a nuke test if the country's leadership gives the order.

The agency also said that the communist state produced 10kg of plutonium at its Yongbyon nuclear reactor last year, and that it is expected to be able to reprocess additional spent fuel rods to produce more fissile material from the end of this year.

The spy agency also said the latest import ban of coal from China will leave 300,000 North Koreans unemployed, making its gross-domestic product contract by 2.5 percentage points.

Specifically, the agency said the China's decision will reduce North Korea's gain of foreign currency by 23 percent, or $78 million.

The NIS also said Kim Won-hong, the former head of Pyongyang's spy agency, has been placed under confinement while around five other senior officials are presumed to have been recently executed by the regime.

The dismissed Kim, 72, was fired as head of the Ministry of State Security in mid-January after the probe by the Workers' Party of Korea found the agency had abused its authority, according to Seoul's unification ministry. His military rank was also demoted to major general from full general, it said.

The NIS then said following the purge, the North Korean leader ordered the relocation of the statute of Kim Jong-il from the agency's headquarters, claiming the organization "does not deserve" the honor.

Seoul's intelligence officer then said there are estimated to be 439 markets in the North, with the penetration of the market system similar to those of Hungary or Poland right before they shifted to a capitalist system. (Yonhap)