Tens of thousands of South Koreans are expected to march in Seoul to demand President Park Geun-hye's resignation on Saturday, a day after she took blame for a "heartbreaking" scandal and rising suspicion that she allowed a mysterious confidante to manipulate power from the shadows.
Police expect around 40,000 people in what could be the largest anti-government rally in nearly a year while organizers say as many as 100,000 will turn out.
Dozens of police buses were parked in streets around City Hall and also a square in front of an old palace gate, which the police plan to close off to prevent protesters from marching toward the Blue House, the presidential office and residence.
Smaller protests have taken place daily in past weeks amid growing calls for Park to step down, although opposition parties have yet to make a serious push for her resignation or impeachment for fears of negatively impacting next year's presidential elections.
In Friday's televised apology, Park vowed to accept a direct investigation into her actions, but the opposition, sensing weakness, immediately threatened to push for her ouster if she doesn't distance herself from domestic affairs and focus on diplomacy, and accept a prime minster chosen by the parliament.
"I feel a huge responsibility (for the scandal) deep in my heart," Park said, her voice shaking. "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 late 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 realize 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 also trying to re-establish 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 released earlier Friday had her approval rating at 5 percent, the lowest for any president in South Korea since the country achieved a democracy in the late 1980s following decades long dictatorships.
"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.