South Korean companies that invested in a now-shuttered joint industrial park in North Korea asked the Seoul government Thursday to allow them to visit the complex to check their factories, officials said.

The move came as North Korea hinted last week that it resumed the operation of the Kaesong Industrial Complex without consent from South Korean firms, which had to leave their properties behind there due to the park's closure in 2016.

A group of about 40 businessmen are hoping to visit the complex, which Seoul shut down in February last year over North Korea's nuclear and missile tests, according to company officials.

"It is not certain whether we can visit the factory zone, but we hope that our move could help improve strained inter-Korean ties if realized," said Shin Han-yong, the head of an emergency committee tackling the complex's shutdown.

The outlook for their trip is murky as North Korea is not likely to consent to their visit amid heightened tensions over Pyongyang's nuclear and missile programs.

"The government will consider whether to approve firms' requests after gauging various factors," an official at Seoul's unification ministry said.

The ministry said that there are no specific signs that confirm North Korea's reopening of the factory zone, though some bus movements and illuminated street lamps have been spotted.

The government said that North Korea should not resume the complex without permission as factories and machinery there belong to the South Korean firms.

It said that if North Korea resumes operations, it would violate inter-Korean agreements banning the random naturalization of Seoul firms' assets. It could also breach the latest UN sanctions barring the North's textile exports if the country seeks outbound shipments.

Opened in 2004, the factory zone had housed 124 South Korean firms employing more than 54,000 North Korean workers to produce labor-intensive goods, such as clothes and utensils.

In retaliation against Seoul's closure of the complex, North Korea kicked out all remaining South Koreans and announced that it would freeze their assets and liquidate them.

Any trip by South Koreans to North Korea requires the Seoul government's approval, as well as the North's consent. The sides still technically remain at war since the 1950-53 Korean War ended in a truce, not a peace treaty. (Yonhap)