Thousands of citizens took to the streets in downtown Seoul on Saturday, demanding President Park Geun-hye step down, in protest of an ongoing influence-peddling scandal surrounding her confidante.

Groups, including the country's largest umbrella labor union, the Korean Confederation of Trade Unions, which had been at odds with the president on a host of issues in the past, jointly held a candlelight rally in Cheonggye Stream Square.

About 20,000 took part in the demonstration, according to the organizers, although the police put the number closer at 9,000, with 8,000 officers mobilized to deal with contingencies. 

Police and politicians have been casting watchful eyes on the rally as it was the first mass movement after the president apologized in a nationally televised address over allegations raised against her confidante, Choi Soon-sil. 

In the apology delivered Tuesday, Park admitted to the leak of dozens of presidential speeches to Choi before they were made public, acknowledging her ties.

Still, the scandal has only been snowballing as a series of media reports claimed Choi's possible intervention in other state affairs, including some related to sensitive policy issues. Choi holds no governmental post. 

A 24-year-old college student, who asked not to be named, said he joined a demonstration as he was "so frustrated and disappointed" about the latest scandal.

 Others like Chris from Australia who works as an English teacher here said it seemed very meaningful that the public came out to send a message to the government. He asked for his last name not to be used for privacy reasons.

Lee Jae-myung, the mayor of Seongnam, located just south of Seoul, and a longtime critic of the administration, joined the demonstration and criticized the president, saying she is "making fun of this democratic country." 

He, however, was one of the very few politicians who took part in the event, as many oppose talk of resignation or impeachment, citing possible political confusion and the need to see what the ongoing investigation will unearth. 

Political leaders have been cautious since an official probe has just started, and it will take time to sort out all the accusations being raised at present. 

Choi, in the center of the uproar, has so far denied all charges of wrongdoing, other than helping the president write speeches, and expressed a wish to cooperate with the investigation.

Choi has even said through her attorney that she will accept any punishment if found guilty of breaking any laws. 

Prosecutors here are currently looking into the case, summoning a number of officials from the government and private companies related to the matter. 

On Saturday, they attempted to raid the offices of presidential aides who are involved in the scandal, but Cheong Wa Dae refused them entry, citing the need to protect state secrets that may be compromised. 

The latest scandal, involving what critics call the "shadow president," has sent Park's approval rating to 17 percent, the lowest point since her inauguration in February 2013, according to local pollster Gallup Korea.

Faced with the scandal, Cheong Wa Dae is widely expected to replace some of her closest aides in a reshuffle early next week. (Yonhap)