North Korea on Friday lifted entry bans it had imposed earlier this week on two South Korean officials involved in managing a jointly-run factory park in the North.

Pyongyang didn't offer a clear explanation on why it banned the officials from the Kaesong industrial park on Wednesday or why it decided to allow them to visit again, said Jeong Joon-Hee, a spokesman from Seoul's Unification Ministry. South Korean employees at Kaesong had commuted normally across the border this week.

The factory park, where about 120 South Korean companies also employ more than 53,000 North Koreans, has been a critical source of income for the cash-strapped North since its establishment in 2004, during an era of rapprochement between the rivals.

One of the men allowed back in, Choi Sang-chul, was the vice chairman of Seoul's management committee overseeing the park. He had been involved in negotiations with the North over wages, taxes and fees. Jeong said Choi plans to visit the factory park on Monday.

The countries struggled for several months over wage levels for North Korean workers employed by South Korean companies at Kaesong before agreeing on a 5 percent increase in minimum wage in August.

The two sides are currently negotiating land usage fees that South Korean companies at Kaesong must pay to North Korea for 2015. Under a previous agreement between the countries, South Korean companies at Kaesong were exempted from land usage fees for 10 years through 2014.

The Koreas are still technically at war because the 1950-53 Korean War ended with an armistice, not a peace treaty.