Former South Korean president Park Geun Hye drew flak yesterday for her "insincere" public apology, as prosecutors questioned her for the first time in a criminal investigation centred on her alleged involvement in a corruption and influence-peddling scandal that caused her downfall.

"I am sorry to our citizens. I will undergo questioning sincerely," she said calmly in front of a media mob after arriving at the Seoul Central District Prosecutor's Office.

It was Ms Park's first public appearance since she moved out of the presidential Blue House on March 12, two days after the Constitutional Court upheld her impeachment by Parliament in December.

Prosecutors said the 65-year-old daughter of the late authoritarian leader Park Chung Hee was composed and responded to questions sincerely but declined to reveal if she denied all charges, as some sources had claimed.

They avoided questions on whether the country's first female president will be arrested, insisting they are focused on the interrogation for the time being.

Ms Park, who is South Korea's first head of state to be removed from office, faces 13 charges, including bribery, abuse of power and leaking government secrets.

If found guilty, she could face up to 45 years in jail, according to some legal experts.

Prosecutors have accused her of colluding with her civilian friend Choi Soon Sil to extort millions of dollars from big conglomerates under the guise of donations to two foundations controlled by Choi.

Ms Park is also accused of abusing her power to allow Choi to meddle in state affairs and leaking official documents to her.

Some 40 people have been indicted in connection to the scandal, including Choi, Samsung heir Lee Jae Yong and Ms Park's former aides.

While Ms Park had apologised to the nation three times in the months prior to her ouster, she has always denied any wrongdoing.

Now stripped of presidential immunity against indictment, she was summoned to face questioning yesterday morning.

Her apology drew criticism, however. The main opposition Democratic Party said Ms Park demonstrated "no remorse".

The minor conservative Bareun Party called her "insincere" comments disappointing.

But the ruling Liberty Korea Party urged prosecutors to show respect for the former president, adding that she "appeared to restrain herself even though she probably had many things to say".

Ms Park, who was accompanied by six lawyers, was interrogated by two senior prosecutors until late in the day. She was given two breaks for lunch and dinner.

A key point of contention is whether the millions of dollars that she is alleged to have requested from the major conglomerates amounts to bribery.

Samsung's Lee, who has been arrested on bribery and embezzlement charges, has insisted that the money was given as a goodwill donation, and not in return for government support for a merger of two Samsung subsidiaries to pave the way for his succession.

"There is a possibility for Park to go to jail but it's a big disgrace for the entire country to have a former president serving a jail term," noted Sogang University's political science professor Kim Jae Chun.

The country is set to choose a new president on May 9, with the Democratic Party's front runner Moon Jae In leading in all opinion polls.