SEOUL, Feb. 10 (Xinhua) -- South Korea's joint military-police investigative body on Tuesday raided 18 locations in its probe into allegations of South Korea's unauthorized civilian drone flights into the Democratic People's Republic of Korea (DPRK), according to Yonhap news agency.

Military and police investigators launched simultaneous raids on 18 sites, including the Defense Intelligence Command and the National Intelligence Service (NIS), from about 9 a.m. local time.

The joint military-police investigation task force investigated three civilian suspects on charges of aiding the enemy, alongside the violation of the aviation safety act.

The task force additionally booked three active-duty military personnel and one NIS official as suspects, believing that they were involved in the unauthorized drone flights.

The DPRK had accused South Korea of violating its airspace by flying a drone on Jan. 4.