Kim is one of the closest aides to Lee and has often been dubbed his "butler." His arrest strongly suggests that an investigation of Lee is forthcoming. Moreover, prosecutors have also reportedly secured a statement from a former NIS official that Lee knew about Kim's taking of NIS money.

Another former presidential secretary to Lee, Kim Jin-mo, was also arrested Tuesday on charges of taking about 50 million won in NIS money. He is suspected of involvement in efforts to silence a whistleblower government official and using the money for that purpose.

"Former President Lee is not coming in today," an aide told reporters waiting in front of Lee's office in Samseong-dong in southern Seoul. "I can't confirm his specific schedule."

Aides to Lee have denounced the prosecution investigation as a political reprisal against the former conservative president by the liberal administration of President Moon Jae-in, and rejected allegations that Lee knew about the NIS money.

Aides had been scheduled to hold a meting at the Samseongdong office, but that meeting has also been called off, according to the office. Still, they are expected to meet somewhere else and could issue a statement on the arrest of Kim. (Yonhap)