South Korea's special prosecutor's office has summoned a Samsung Electronics executive for questioning as it investigates a widening influence-peddling scandal that has embroiled President Park Geun-hye.

The office said it had summoned executive vice president Hwang Sung-soo for questioning on Friday, adding he was classified as a witness. It did not elaborate.

Hwang is the fifth executive of Samsung Group, the country's top conglomerate, the prosecutor has summoned. Samsung Electronics is the flagship company of Samsung Group and is the world's top manufacturer of smartphones, memory chips and flat-screen televisions.

A Samsung Group spokesman declined to comment.

Samsung Group leader Jay Y. Lee and vice chairman Choi Gee-sung have been classified as suspects by the prosecution, which has been investigating whether the conglomerate paid bribes to Park's confidant, Choi Soon-sil, to win support from the National Pension Service for the 2015 merger of two Samsung Group affiliates.

Park, 64, was impeached last month by parliament over allegations that she allowed her friend, Choi, to exert inappropriate influence over state affairs.

Choi is accused of colluding with Park to pressure big businesses to contribute to non-profit foundations backing the president's initiatives and is in detention as she undergoes trial.

Both have denied wrongdoing, although Park has apologised for exercising poor judgment.

Prosecutors accused Samsung chief Lee of paying bribes totaling 43 billion won (A$49 million) to organisations linked to Choi to secure the 2015 merger of Samsung C&T and Cheil Industries.

Samsung has acknowledged making contributions to entities controlled by Choi but has denied accusations of lobbying to push through the merger.

The special prosecutor's office last week said it had evidence that Park and Choi shared profits gained through bribery payments, but did not elaborate.

If the impeachment vote is upheld by the constitutional court, Park will become South Korea's first democratically elected leader of South Korea to be forced from office.

The prosecution suffered a blow on Thursday when a Seoul court denied its request for an arrest warrant against Lee, who has helmed the smartphones-to-biopharmaceuticals empire after his father and founding family patriarch Lee Kun-hee was incapacitated by a 2014 heart attack.

Earlier on Friday, the special prosecution said it was mulling whether to make another arrest warrant request for the 48-year-old Samsung chief. While the prosecution has said it would not seek arrest warrants for other Samsung executives, the office's spokesman said that position could change.