Special prosecutors on Monday questioned a former aide of President Park Geun-hye over suspicions she received treatment from medical personnel without due security checks, as part of their probe into a corruption scandal rocking the country.

Ahn Bong-geun, a former presidential secretary for public relations, appeared at the special counsel team's office in southern Seoul. It was his first public appearance in three months since he underwent state prosecutors' questioning over the scandal centered on Park and her friend Choi Soon-sil.

Ahn has rejected summons to testify before the Constitutional Court' hearings on the president's impeachment.

Investigators suspect that Ahn helped Choi and others, such as therapists, freely enter the presidential office Cheong Wa Dae without leaving official records.

He declined to comment on the allegations as he entered the building.

Ahn is among three ex-presidential officials dubbed Park's "doorknob" secretaries for their close relations with the president. Jeong Ho-song, one of the officials, is currently standing trial over allegations he leaked government secrets to Choi and let her intervene in making key decisions. Choi had no policy experience nor held any official post in the Park administration.

On Tuesday, the Seoul Central District Court will hold a hearing to decide the legality of arresting Woo Byung-woo, a former senior presidential secretary for civil affairs. Woo is accused of abusing his power in relation to the government's personnel management and the prosecution's investigations.

The probe team, led by Independent Counsel Park Young-soo, has been accelerating its investigation as the set deadline approaches on Feb. 28.

The special counsel has asked Acting President and Prime Minister Hwang Kyo-ahn to extend the investigation period for a month, but it is yet unclear whether he will approve the request. (Yonhap)