South Korea will hold presidential election on 9 May, 2017 to elect its next leader following the impeachment of Park Geun-hye.
Prosecutors said Wednesday they have summoned former President Park Geun-hye to attend a questioning on March 21 to be grilled as a suspect in an abuse of power and corruption scandal.
Park's presidency formally ended Friday, when the Constitutional Court approved the National Assembly's vote to impeach her in December.
Prosecutors plan to question Park next week over suspicions that she colluded with a friend to extort money and favors from companies and allowed the friend to secretly interfere with state affairs.
The special election was announced following the downfall of Park, the first female South Korean leader.
Her neighbours gave her a pair of Jindo dogs, a Korean breed of hunting dogs, when she left for the presidential Blue House in 2013. Exiting the Blue House on Sunday, Park said, "Though it may take time, I believe the truth will eventually prevail".
The conservative Dong-A Ilbo daily, which long supported Park, said in a front-page headline: "To the last... there was no word of acceptance" of the ruling.
Similarly the Constitutional Court asked her to appear before it as it held a series of hearings while considering whether to confirm or overturn her impeachment by parliament, but she did not do so.
Prime Minister Hwang Kyo Ahn, who has also been acting president since December, had said earlier that he would not run for the post. She has denied any legal wrongdoing and expressed defiance toward her corruption allegations.
Park, who had already been impeached by the parliament late a year ago, had repeatedly refused to be questioned by the prosecutors, citing her constitutional impunity as sitting president.
Opinion polls show Mr Hwang as a top conservative candidate even though he has not declared his intention to run.
Samsung denies any wrongdoing. She will fully cooperate with the investigation, Yonhap News reported, citing one of her lawyers.
Choi is now on trial for bribery and extortion, as is Lee Jae-yong, the de facto head of Samsung.
"This is an unacceptable behaviour, after her scandal left the country's reputation deeply tarnished and South Koreans deeply traumatised", he said.