South Korea's 2016 decision to shut down an inter-Korean industrial complex is presumed to have dealt a heavy blow to North Korea's nuclear and missile programs, a government official said Friday.

The statement comes on the first anniversary of Seoul's closure of the Kaesong Industrial Complex in North Korea's border city of the same name in response to Pyongyang's nuclear and missile tests early last year.

Seoul's unification ministry said that the shutdown of the complex had led major countries, including the United States, Japan and the European Union, to strengthen their unilateral sanctions.

"It also played a critical part in allowing the international community to slap tougher sanctions against the North," Jeong Joon-hee, a ministry spokesman, told a press briefing.

Seoul's decision was based on the judgment that the money generated from the complex was suspected of being used to bankroll Pyongyang's nuclear and missile programs.

The government said that since the zone's opening in 2004, around $560 million in total had been paid in wages to North Korean workers.

"We could reasonably assume that the factory park's closure would have taken a heavy toll on North Korea's nuclear and missile developments," Jeong said, saying that the decision cut off cash inflows into the North worth $100 million annually.

"The government thinks that international sanctions probably also hampered North Korea's projects," he said.

A possible resumption of the factory zone is emerging as a key issue in the political arena as liberal presidential hopefuls are voicing the need to reopen it to improve strained inter-Korean ties.  

The ministry said that North Korea's commitment to ending its nuclear and missile programs should be prioritized before talking about whether Seoul should reopen the shuttered complex.

Jeong said that given the grave security situation on the Korean Peninsula, it is not right to assume a flexible attitude toward the resumption of the factory park's operation.

The government earlier expressed concerns that the resumption could spark a row over the violation of the latest UN sanctions resolutions against North Korea.

The factory zone, once touted as the beacon of inter-Korean reconciliation, had housed a total of 124 South Korean firms, with more than 54,000 North Korean workers being employed to produce labor-intensive goods, such as clothes and utensils. (Yonhap)