Samsung Group leader Jay Y. Lee appeared at the South Korean special prosecutor's office on Thursday for questioning on suspicion of bribery in an influence-peddling scandal that may force President Park Geun-hye from office.
The country's top conglomerate has become important in the investigation of Park, who was impeached by parliament in December over the corruption scandal. She would be the country's first democratically elected leader to be removed from office early if the Constitutional Court upholds the impeachment.
Park has denied wrongdoing.
"I am very sorry to the South Korean people for not showing a better side," Lee told reporters as he arrived at the prosecution office in a black Korean-made Ssangyong sedan, greeted by protesters holding signs calling for his arrest and accusing him of being the president's accomplice.
Parliament impeached Park over allegations she allowed a friend, Choi Soon-sil, to exert inappropriate influence over state affairs.