South Korean President Park Geun-hye is suspected of having conspiring with her longtime confidante and former aides, who were indicted on Sunday for multiple charges, prosecutors said in an interim announcement of investigation results.

Park has a complicity "to a significant extent" with the three criminal suspects in multiple offenses, the head of a special investigative unit in the Seoul Central District Prosecutors' Office in charge of the case told a nationally televised press conference.

The announcement indicated the prosecution office regards President Park as a criminal suspect in its investigation. The special unit chief said such interim results are based on comprehensive evidence documents collected by prosecutors.

Park, however, cannot be indicted for criminal charges as the country's constitution bans a sitting president from being criminally charged until a single, five-year term ends, according to the prosecution office.