South Korean lawmakers are questioning leaders of the country’s biggest businesses in a rare televised hearing as part of a huge corruption inquiry.
Samsung, Hyundai and six other firms admitted giving millions of dollars to funds linked to President Park Geun-hye, but denied seeking favours.
Samsung admitted to giving the daughter of Ms Park’s friend an expensive horse.
Parliament is due to vote on Friday on Ms Park’s impeachment over her involvement in the scandal.
Massive protests have been held in recent weeks demanding her resignation.
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The executives are being questioned by a cross-party committee of lawmakers. The panel has no power to punish but its chairman has said the hearing is a place for apology.
One of the corporate bosses acknowledged that it was difficult for firms to say no to government requests.
“It’s a South Korean reality that if there is a government request, it is difficult for companies to decline,” said Huh Chang-soo, head of the GS Group and chairman of the Federation of Korean Industries lobby group.
The conglomerates all gave large donations to non-profit foundations operated by Choi Soon-sil, a close confidante of Ms Park.
Ms Choi has been charged with coercion and attempted fraud.
Hard questions: Stephen Evans, BBC News, Seoul
These are men who never appear in public if they can help it. They normally live in an enclave of power and wealth, hidden behind the shaded glass of chauffeur-driven black cars.
But they filed in, each in their corporate uniform of a dark suit. They raised their right hands and promised to tell the truth. And then they were subject to what they are not used to: hard questions which some might deem impertinent.
The hearing has the air of a spectacle because press photographers have been allowed to stay and they crane towards the business titans from ladders, constantly firing off loud barrages of clicks.
The de-facto head of Samsung, Lee Jae-yong, seemed discomfited by questioning. His eyes moistened when his bed-ridden father was mentioned. And he gulped when asked how much inheritance tax he had paid. He didn’t know, he said.
He did defend donations to funds controlled by a friend of the president, saying his company often gave money to what seemed like a good cause.
Lawmakers spent the most time grilling Mr Lee. Samsung has been accused of giving donations in exchange for support of a controversial merger that effectively strengthened his position in the company.
The company gave a total of 20.4 billion won ($17.46 million) to the two foundations.
Like the other leaders, Mr Lee denied the allegations, saying Samsung “never provided support or gave donations in return for something”.
But he admitted that his company provided a one billion won (£670,000, $855,000) horse to Ms Choi’s daughter, a professional equestrian, and said he regretted it.
Mr Lee apologised for Samsung’s involvement in the scandal and said his company would “take all responsibility” if there was any.
South Korea’s family-owned conglomerates, known as chaebols, have increasingly been perceived as a symbol of the out-of-touch elite, and have become a target of public fury in recent protests calling for Ms Park’s resignation.
Ms Park has apologised multiple times to the public for allowing Ms Choi inappropriate access to government decisions but has stopped short of resigning.
Last week she said she would leave it to parliament to decide her fate, and on Tuesday she was quoted by her party’s leader as saying she would accept the outcome of Friday’s impeachment vote.
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