North Korea is holding a South Korean worker at a joint factory park for allegedly denouncing the North's political system and inciting female North Korean employees to flee their country, officials said Monday.

North Korea sent a message early Monday stating it was investigating the South Korean worker but would guarantee the person's safety, according to the South Korean Unification Ministry, which handles relations with the North.

Ministry spokeswoman Lee Jong-joo told reporters that the ministry has asked the North to provide the South with details of the incident.

According to Lee, the North said the South Korean denounced the country's political system, and that an investigation was taking place under an inter-Korean accord on the business complex in the North Korean border town of Kaesong.

Later Monday, a senior ministry official told reporters that the North also accused the South Korean worker of "corrupting" female North Korean workers at Kaesong and "instigating" them to defect from the North, according to the ministry. The official declined to give his name, citing department policy, it said.

Lee said it is not the first time the North has held South Koreans at the industrial zone at the Kaesong complex.

She didn't provide further details, including the identity of the worker being held.

In a separate case, two female American journalists have also been held in North Korea since they allegedly crossed the border from China on March 17 while reporting on North Korean refugees. The U.S. State Department said last week that North Korea has assured U.S. officials the journalists working for San Francisco-based Current TV would be treated well.

Monday's detention also came amid heightened tension on the Korean peninsula with the North planning to launch a satellite into orbit sometime between April 4 and April 8. Regional powers suspect the North is trying to test a long-range missile capable of reaching Alaska, and have warned the launch would trigger international sanctions.

The Kaesong complex has been considered a promising example of inter-Korean cooperation after decades of animosity, and a key source of hard currency for the impoverished North.

Relations between the Koreas have deteriorated steadily since a pro-U.S., conservative government took office in Seoul last year with a new, tough policy toward the North. Pyongyang has responded by cutting ties, halted key joint projects and significantly restricted border traffic.

Earlier this month, the North closed the border several times in protest of South Korea's annual military training with the U.S., stranding hundreds of South Korean workers working at Kaesong.