Ousted and jailed former President Park Geun-hye was additionally charged for carrying out illegal opinion polls ahead of the 2016 general elections in a bid to nominate those friendly toward her as legislator candidates, prosecutors said Thursday.

The Seoul Central District Prosecutors' Office said it indicted her on the count of violating the election law. She is suspected of involvement in conducting 120 surveys to canvass opinion in Gangnam, southern Seoul, and Daegu -- both conservative strongholds -- before the April 13 vote.

Prosecutors believe that the polls were carried out in order for the Park government to register so-called pro-Park figures as candidates so as to tighten her grip on power.

The new indictment puts her on trial for 21 different criminal charges. She has already been under pre-sentencing detention since April last year on multiple corruption charges over an influence-peddling scandal that removed her from office in March.

Prosecutors brought more bribery charges against her early this month for taking 3.65 billion won ($3.4 million) from the National Intelligence Service and using it personally. They suspect that Park spent some of the illegal NIS funds to cover the poll expenses.

Prosecutors have also indicted two of Park's ex-senior presidential secretaries for the same charge and bribery in connection with the illegal opinion polls. A senior NIS official in charge of the budget at that time will also stand trial for his involvement in the illicit political activity on the charge of loss of state funds, prosecutors said.(Yonhap)