Choi Soon-sil, known as the South Korean "Rasputin" and mastermind of the corruption scandal that has shaken South Korea, appeared at the Constitutional Court on Monday to testify in a hearing on the impeachment of President Park Geun-hye.

Choi, 60, who has been imprisoned since November over the scandal, was heavily escorted as she arrived at the court and did not answer any questions from South Korean media, Yonhap news agency reported.

Today's hearing is the fifth session of Park's impeachment trial, after the National Assembly on Dec. 9 passed a motion to impeach the president on suspicions that she cooperated with her close friend Choi to hatch a plot to extort large business groups.

Choi has denied the charges before parliament as well as the criminal court investigating the case, which includes charges of abuse of power, extortion and attempted fraud.

Prosecutors investigating the scandal say Choi, with assistance from Park, extorted major conglomerates to transfer some 77.4 billion won (about $65 million) to two foundations that she controlled.

The case has also prompted the prosecutor's office to investigate Samsung, South Korea's largest business group, for its cooperation with the network of favors allegedly orchestrated by Choi. Investigators will also decide whether to issue an arrest warrant for company heir Lee Jae-yong.

The South Korean Constitutional Court has until early June to ratify or reject the impeachment of Park approved by parliament.

If it is approved, presidential elections will be held within 60 days from the date of the verdict.