SEOUL — South Korean President Park Geun-hye took sole blame Friday for a ‘‘heartbreaking’’ scandal that threatens her government and vowed she will accept a direct investigation into her actions amid rising suspicion that she allowed a mysterious confidante to manipulate power from the shadows.

In a high-stakes address to the nation, Park, her voice shaking, said the scandal is ‘‘all my fault and mistake.’’ In an extraordinary moment, she also denied media speculation that she had been controlled by a religious cult.

‘‘I feel a huge responsibility (for the scandal) deep in my heart,’’ Park said. ‘‘It is all my fault and mistake.’’

As calls for her to resign rise, Park is attempting to show the contrition and sense of responsibility that South Koreans demand while re-establishing her tarnished credibility. She is in the fourth year of a single five-year term and, even before this scandal, faced criticism over the government’s response to a ferry sinking that killed more than 300 and a perceived aloof nature.

One national poll had her approval rating at 5 percent, the lowest for any modern South Korean leader.

Last week Park surprised many when she acknowledged that she had relied on Choi Soon-sil, the daughter of a cult leader and Park mentor, for help editing presidential speeches and other undefined ‘‘public relations’’ issues.

Anger has exploded in the days since, with media reports claiming that the influence Choi had went much deeper. There are reports that Choi reviewed and made recommendations on government policy papers and helped choose presidential aides.

Thousands have protested, Park has fired many of her senior aides.

Choi, 60, was arrested Thursday on a warrant citing alleged abuse of authority and fraud.

Associated Press