The Democratic People's Republic of Korea (DPRK) said on Friday an investigation into a detained South Korean worker is being conducted, according to the official news agency KCNA.

The worker was accused of slandering the system of the DPRK, perpetrating grave acts of infringement against its sovereignty and violating the law, a spokesman for the Central Special Zone Development Guidance Bureau, said, Xinhua reported.

The detainee, Yu Song Jin, is an employee of the Kaesong office of Hyundai Asan, the spokesman said.

The Kaesong industrial park is a joint project developed by the DPRK and South Korea.

The spokesman also said claims by Seoul that the detention of Yu violated project agreements and was abuse of human rights was illogical,  and would only make the situation graver, and unfavorable for the project.

He said if the South Korean authorities continued doing that, they would be accountable for all the consequences.

The DPRK detained Yu on March 30. South Korea has demanded the DPRK release Yu.