Three former heads of the state spy agency face arrest as prosecutors filed for court warrants Tuesday against two of the accused over allegations they paid billions of won of the agency's off-book funds to two aides of then-President Park Geun-hye.

Nam Jae-joon and Lee Byong-ho, who headed the National Intelligence Service (NIS) between 2013-2017, stand accused of being involved in the NIS' regular payments of at least 40 billion won ($3.57 million) to Ahn Bong-geun and Lee Jae-man, two senior secretaries to Park from 2013 to 2016.

Separately, Nam is also suspected of pressuring top officials at Hyundai Kia Automotive Group, the country's largest carmaker, into giving business deals worth 2.6 billion won to a company in connection with a conservative activist group. The money is believed to have been funneled into the advocate group to carry out political activities in favor of the government.

Nam has apparently denied such allegations.

The request for their arrest warrants come on the heels of a Seoul court's granting of a detention warrant on Lee Byung-kee, another ex-NIS chief who served his term under Park, over the same allegations. The prosecutors' office said it is considering applying for an arrest warrant for Lee as well.

Prosecutors grilled Lee Byung-kee on Monday over the suspicions. They believe the money was channeled into a secret fund for Park and used for illegal political activities including conducting an election poll for the conservative bloc, or even by her personally.

He also served as Park's chief of staff before she was ousted in March this year over a massive corruption scandal.

Prosecutors have also called in the other two for questioning.

All of them have apparently told prosecutors to the effect that they "could not reject Cheong Wa Dae's call," deeming the payments were a presidential request.

Park's two aides have been arrested over bribery charges. (Yonhap)