South Korea prez Park Geun-Hye at the Blue House. Pic/AFP

Seoul: South Korean President Park Geun-Hye yesterday agreed to be questioned in a formal corruption probe, portraying herself as an over-trusting, "lonely" leader who dropped her guard with a close friend arrested for fraud.

In a televised address to the nation, Park said the scandal involving her confidante Choi Soon-Sil was "all my fault", but denied reports linking her and Choi to a religious cult.

The scandal has shattered public trust in Park's presidency, and a new Gallup poll showed her approval rating had plummeted to just five per cent — an all-time low for a sitting South Korean president.

"These latest developments are all my fault and caused by my carelessness," Park said, adding that she had suffered "excruciating heartbreak" for being the cause of so much public concern and distress.

An investigation is focused on allegations that Choi (60) leveraged her relationship with Park to coerce local firms into donating large sums to dubious non-profit foundations that she used for her gain.

"If necessary, I am willing to respond to prosecutors' investigations," Park said.