Some 120 North Korean prisoners have escaped a political concentration camp in the northeast of the country and security officials in the area are on high alert, news reports said.
The prisoners escaped the concentration camp in Hwasong, North Hamgyong, a province close to the Chinese and Russian borders, in December, the Dong-a Ilbo newspaper reported Wednesday.
Daily NK, a Seoul-based Internet news site focusing on North Korea, also carried a similar report on Tuesday.
Both reports cited multiple unnamed sources in North Korea.
An official at South Korea's Unification Ministry, which deals with North Korean affairs, said he was unable to confirm the reports, but questioned their reliability. The official spoke on customary condition of anonymity.
News leaked from the reclusive North is usually hard to confirm, which shuns outside access.
The Daily NK report said the area was put in a "state of emergency" after the prison break, which it said was unprecedented, the AP reports.
North Korean authorities have since tightened inspection in Hwasong and adjacent cities to catch the fugitives, of whom 21 have so far been caught, the report said. Most of the escapees caught were found in China and sent back to the communist North after failed attempts to defect to South Korea, it added.
The Hwasong prison camp - located deep inside a mountain and encircled by high wire fences - holds about 10,000 prisoners, Daily NK said. The escape seemed to have been carefully planned with outside help as the escapees drove off in a vehicle waiting outside the prison, according to the report.
Between 150,000 and 200,000 people are believed to be held in prison camps in the communist North for political reasons, according to U.S. government data.