Seoul — In an extraordinary display of abject apology during a moment of supreme crisis, South Korean President Park Geun-hye took sole blame on Friday for a "heart-breaking" scandal amid rising suspicion that she allowed a mysterious confidante to manipulate power from the shadows.Park also vowed to accept a direct investigation into her actions, but the opposition, sensing weakness, immediately said that if she doesn't accept a prime minster chosen by the parliament and withdraw from dealing with domestic affairs, it will push for her ouster."I feel a huge responsibility [for the scandal] deep in my heart," Park said, her voice shaking during the high-stakes televised address to the nation over a scandal that threatens her rule. "It is all my fault and mistake."Park's comments were rife with astonishing moments, and included a frank assessment of her relationship with the woman at the heart of the scandal, Choi Soon-sil, the daughter of a cult leader and a longtime friend of Park's."I put too much faith in a personal relationship and didn't look carefully at what was happening," Park said. "Sad thoughts trouble my sleep at night. I realise that whatever I do, it will be difficult to mend the hearts of the people, and then I feel a sense of shame and ask myself, 'Is this the reason I became president?'"In another exceptional moment, Park denied media speculation that she had "fallen into worshipping cult religions or that shamanistic rituals were held at the presidential Blue House".Her comments come at what may well prove to be the crucial moment of her presidency. 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 faced criticism even before this scandal, particularly for the government's response to a 2014 ferry sinking that killed more than 300 people.One national poll had her approval rating at 5%, the lowest for any leader in South Korea's 68-year history."Anyone found by the current investigation to have done something wrong must be held responsible for what they have done, and I am also ready to face any responsibility," Park said. "If necessary, I'm determined to let prosecutors investigate me and accept an investigation by an independent counsel too."Last week Park surprised many when she acknowledged that she had relied on Choi 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, helped choose presidential aides and even picked out Park's wardrobe.Thousands have protested. Park has fired many of her senior aides and is replacing her prime minister.On Thursday, Park's choice for prime minister, Kim Byong-joon, said at a news conference that he thinks it's possible to have Park investigated, though he said the procedures and methods of any probe of the head of state must be carefully handled.