Samsung Group leader Jay Y. Lee appeared at the South Korean special prosecutor's office on Monday for questioning as part of a wider investigation into an influence-peddling scandal that could topple President Park Geun-hye.
Lee is accused of pledging 43 billion won ($37.31 million) to a business and organisations backed by Park's friend, Choi Soon-sil, in exchange for support for a 2015 merger of two Samsung companies.
Park, Lee, Choi, and Samsung Group have all denied bribery charges.
Proving illicit dealings between Park or her confidantes and Samsung Group is critical for the special prosecutor's case that ultimately targets Park, analysts say. Park was impeached by parliament in December.
Lee arrived at the prosecution office in southern Seoul early on Monday in a black sedan, dressed in a dark blue suit and tie and flanked by Samsung Group officials and his lawyer.
"I will once again tell the truth to the special prosecution," Lee told reporters before entering an elevator.
Outside the prosecutor's office, protesters held up signs calling for his arrest.
Investigators are mulling whether to seek another arrest warrant against the 48-year-old executive, a suspect in a probe into the graft scandal that led to parliament's impeachment of Park. South Korea's Constitutional Court is deliberating whether to uphold that impeachment.
In January, the special prosecution sought an arrest warrant against Lee after questioning him for more than 22 hours, charging him with paying bribes to win the state pension fund's support for the controversial merger of Samsung C&T and Cheil Industries.
A Seoul court however rejected that request for an arrest warrant.