The presidential office on Thursday confirmed that six South Korean nationals have been detained in North Korea and vowed to make efforts to secure the release of them by swiftly resuming talks with Pyongyang. The six citizens, including three North Koreans who had defected to South Korea, have been held in the North on charges of espionage and others since between 2013 and 2016. They include three missionaries arrested by the North Korean authorities from 2013 and 2014, namely Kim Jung -wook,