SEOUL, Korea, Republic Of -- It's a rare moment of public reckoning for South Korea's most powerful business leaders, courtesy of the country's biggest political scandal in years.

Usually cloistered executives from Samsung, Hyundai Motor and six other companies faced grilling Tuesday as lawmakers looked into their links to prosecution claims that South Korean President Park Geun-hye allowed a corrupt confidante to pull government strings and extort companies.

It is unusual for tycoons such as Samsung Electronics Vice Chairman Lee Jae-yong, Hyundai Motor Chair Chung Mong-koo and SK Group Chair Chey Tae-won to face public questioning. Major TV channels broadcast live the hearing that is expected to go on all day.

Park's scandal has increased doubts over deep ties between politicians and the country's top family-controlled businesses, known as chaebol. The South Korean president faces allegations she played a role when big business groups donated funds for non-profit foundations under the control of Park's confidante Choi Soon-sil. Prosecutors are reportedly looking into whether some of the 53 businesses that donated funds received any favours in return.

Many protesters who have filled Seoul streets calling for Park's arrest have also vented anger toward the chaebol and their founding families, shouting they are accomplices in the scandal.

During the questioning, Samsung's Lee and other chaebol bosses denied that they donated the funds to the foundations in order to receive any favours from the government.

Samsung's Lee faced most of the questions from both ruling and opposition party lawmakers as the group donated the biggest amount of money to the non-profit foundations and also because it was the only group that sponsored the Choi family outside the foundations. They tried to get Lee's answers on who at Samsung made decisions to sponsor the Choi family but Lee evaded answers.

Lawmakers also grilled the 48-year-old heir regarding his one-on-one meetings with President Park, its business deal with the Choi family-owned company and a contentious merger of two Samsung companies last year. Lee admitted that the way Samsung sponsored Choi's daughter was not appropriate and that he regrets it.

But most of the time, he answered that he was not aware of it or could not recall details. When asked about how he first knew the secretive confidante of the president, the Samsung leader said he cannot remember.

"I heard many times (about Choi) recently and I learned how (Samsung) supported as I confirmed the facts but I'm really sorry lawmaker that I don't know when I first learned (about Choi)," he said.

Some lawmakers' questions went beyond the scandal to other issues such as Samsung semiconductor workers who fell gravely ill and how Lee accumulated wealth. Park Young-sun, an opposition party lawmaker, grilled Lee on how much tax he paid since he received 6 billion won ($5.1 million) from his father 20 years ago, which snowballed to 8 trillion won ($6.8 billion) through complicated business dealings within Samsung and initial offerings of Samsung companies.

Another opposition lawmaker, Sohn Hye-won, questioned the role of a secretive corporate strategy office at Samsung, which allegedly makes key decisions for Samsung companies but do not have legal responsibility for the decisions they make.

Instead of answering specifically to the questions from lawmakers, Lee repeatedly apologized for disappointing the public without naming what he was apologizing for.

"There are many things that I myself feel embarrassed about and I regret as we have disappointed the public with many disgraceful things," Lee told lawmakers.