An American teacher was detained in North Korea over the weekend, raising to four the number of U.S. citizens now being held by the communist nation's authoritarian regime.

Kim Hak-song had worked at the Pyongyang University of Science and Technology, the same school where American Tony Kim had worked prior to being arrested at Pyongyang International Airport two weeks ago, North Korea's state-run KCNA news agency said Sunday.

Few details on Kim Hak-song or his arrest were immediately available. KCNA said he was detained Saturday on suspicion of committing “hostile acts."

North Korea confirmed Wednesday that it has detained Tony Kim, who was seized April 22 as he tried to leave the country. Tony Kim, who taught accounting and other courses, is accused of attempting to overthrow the government.

"He was intercepted for committing criminal acts of hostility aimed to overturn the DPRK not only in the past but also during his last stay before interception," KCNA said in confirming reports of Tony Kim's arrest. DPRK is the acronym for the Democratic People's Republic of Korea.