A prototype of the KF-21 fighter jet prepares for a test flight at the headquarters of Korea Aerospace Industries in Sacheon, South Gyeongsang Province, May 10, 2023. Joint Press Corps

The Korean military, police and the National Intelligence Service launched a joint investigation into a Telegram channel that claims to be "selling technology documents" of the KF-21 fighter jet and the KUH-1 Surion helicopter, both of which were manufactured by Korea Aerospace Industries (KAI).

According to military officials Monday, the joint investigation team is looking into the Telegram channel which has been uploading messages that it "sells classified military information" since August.

The channel's operator reportedly posted in February that they had "collaborators within the military and the Agency for Defense Development," saying that they are selling documents related to Korea's first home-developed utility helicopter, the Surion, uploading photos presumed to be of some helicopter parts.

The operator was also reported to have said to have "secured technology documents of the KF-21" which they will sell "after finishing our own cross-check process." The operator also said it has documents related to the Freedom Shield joint military exercise between Korea and the United States.

A KUH-1 Surion Helicopter flies at the headquarters of Korea Aerospace Industries in Sacheon, South Gyeongsang Province, May 27. Courtesy of Army

Counterintelligence authorities are investigating the identity of the Telegram channel operator and whether the channel actually possesses military secrets. If they determine that the claims are genuine military secrets, the authorities will request a formal police investigation.

The Defense Technology Security Act stipulates that acquiring, using or disclosing defense industry technology through illicit means shall be punished with imprisonment for up to 10 years or fines up to 1 billion won ($720,000).

Separately, the Defense Acquisition Program Administration (DAPA) said, Monday, it has completed the operational deployment of theSurion to the Army.

The helicopter began being delivered to the Army in late 2012, after a seven-year development period starting in 2006. It was designed to replace the Army's aging fleet of U.S.-made UH-1H and 500MD helicopters.

The Army now operates more than 200 Surions, which carry out various operations, including air assault and cargo airlift missions.

The helicopter has a maximum air speed of 146 knots and can carry up to 13 people, including two pilots, according to KAI.