South Korean prosecutors on Wednesday widened its ongoing investigation into a scandal involving President Park Geun-hye's longtime confidante, Choi Soon-sil, China's Xinhua news agency reported.

Investigators raided the homes of two former key aides to the embattled president on alleged involvement into Choi's influence peddling and the leakage of confidential presidential documents to the 60-year-old private citizen.

Computer hard discs, diaries and mobile phones were seized from the homes of Lee Jae-man and Ahn Bong-geun, former presidential secretaries who had assisted President Park for about two decades together with Jeong Ho-seong.

Jeong has been placed under custody for allegations that he had brought secret presidential reports on defence, diplomatic and economic affairs to Choi on a daily basis.

The three aides are dubbed "three knobs of a door" that lead directly into President Park thanks to their longtime assistance.

Choi Soon-sil, whose friendship with the president dates back to the mid-1970s, is suspected of exercising undue influence for personal gains and meddling in state affairs from the shadows though she has no public position.

Choi has been formally arrested since she came back to Seoul in late October.

The woman had stayed in Europe for about two months before coming back to her home country.

Public attention is centered on whether prosecutors investigate President Park, who said last Friday that she would accept a direct probe into herself "if necessary."

Local media reports estimated that prosecutors would decide next week on whether to investigate the president. -- BERNAMA