North Korea has promised to close one of core facilities of its nuclear program ahead of its historic summits with the South and the United States. 

Pyongyang on Saturday announced that it will suspend nuclear and missile tests and dismantle the Punggye-ri nuclear test site in the northeastern province.

The Punggye-ri region has remained under constant satellite surveillance by the global intelligence community. Last month, the U.S.-based North Korean analysis website 38 North reported, based on satellite imagery, that the site has a shown a significant slowing in tunneling and other operations.

The organization assessed that the reduction in activity could be attributed to recent diplomacy between Pyongyang and Seoul and Washington.

"It appears that the North is trying to show that its proposal to denuclearize is not an empty promise," Yang Moo-jin, a professor at the University of North Korean studies, said.

The North Korean government has maintained strict control over the region, reportedly relocating residents to other regions due to risk of radioactive poisoning. There has been speculation in the past that the region and its surrounding areas may have been contaminated with radioactive materials.

The head of South Korea's weather agency, Korea Meteorological Administration, warned last year during a parliamentary meeting that another nuclear blast could trigger a collapse of the North's mountainous test site and a leak of radioactive materials.

Geological experts have raised concerns that the site's nuclear tests may have influenced volcanic activities in the nearby Mt.Paekdu, which can lead to serious environmental consequences.

Experts have warned that the North's nuclear test site could have become fatigued and unstable from six nuclear tests that a collapse could happen at any time. A Japanese new outlet reported in October of last year that a tunnel under construction at the site collapsed and as many as 200 workers could have been killed.

The report has not been substantiated. (Yonhap)