South Korean prosecutors said on Sunday that they believe President Park Geun-hye was an accomplice in a corruption scandal that has rocked her administration, in a heavy blow to her fight for political survival.

The prosecutors' comments, which came as they indicted a close friend of Park's and two of her former aides, are likely to spur stronger calls for her to step down or be impeached.

Park's close friend Choi Soon-sil and former presidential aide An Chong-bum were charged with abuse of power in pressuring companies to contribute funds to foundations at the center of the scandal, said Lee Young-ryeol, head of the Seoul Central District Prosecutors' Office.