Personal email accounts of high-ranking officials at the defense ministry and the military have been targeted in a suspected North Korean hacking attack.

According to authorities on Tuesday, the security investigation unit at the National Office of Investigation(NOI) under the National Police Agency has launched an investigation involving officials as high up as the vice-ministerial level.

An official at the police agency said the probe is under way, but declined to share details on the targets and the scope of damage.

The defense ministry said the email accounts in question are personal accounts and none are linked to an intranet or a military server. The ministry has established a special task force to investigate the matter.

The personal accounts of over 100 South Koreans, including military officials and national security experts, have reportedly been subject to the latest hacking attack.