Korea Aerospace Industries(KAI), South Korea's sole aircraft manufacturer, has been the target of two cyberattacks this year, and many documents are believed to have been leaked.

According to various government sources on Wednesday, the hackers even accessed some of KAI's internal systems.

Some suggested sensitive information on the KF-21 fighter jet, FA-50 light combat aircraft, unmanned aircraft and radar may have been breached.

Without elaboration, the agency confirmed that it had filed for a police investigation on Monday.

Main opposition People Power Party(PPP) Rep. Ha Tae-keung said the Defense Acquisition Program Administration(DAPA), which handles national arms procurement, confirmed the hacking incidents.

Ha, a member of the parliamentary intelligence committee, also suggested that blueprints of the KF-21 jet may have been taken by the hackers.