Over one-third of lawmakers-elect who won at this week's parliamentary polls have been booked for election-related offenses, up sharply from the 2012 polls, prosecutors said Thursday.

A total of 104 lawmakers-elect out of the 300-member National Assembly have been booked for charges related to irregular election campaign activities as of Wednesday, according to the Supreme Prosecutors' Office (SPO).

The number is up 31.6 percent from 79 lawmakers-elect who were booked during the same period in the 2012 parliamentary elections.

Of the booked candidates who gained victory at Wednesday's polls, 98 are being investigated. Prosecutors said they indicted one suspect and freed five others.

Some 53.9 percent, or 56 politicians, have been caught for negative campaigning, followed by bribery with 22.1 percent. It said 6.7 percent were caught because they used unauthorized methods to sway votes.

Prosecutors said the method of election violations have been clearly shifting from bribery to spreading lies.

The total number of people booked on charges of election-related offenses during this year's general elections reached 1,451 so far, with 31 people currently in custody. The figure is up 32.4 percent from that of the previous general elections which stood at 1,096.

In the latest elections, the main opposition Minjoo Party and the People's Party won 123 and 38 seats, respectively. The ruling Saenuri Party secured just 122 seats, marking the first time in 16 years for a ruling party to fail winning a parliamentary majority.

The rest of the seats went to another minor opposition, the Justice Party, and independents.

Prosecutors vowed to take stern measures against all election law violations by carrying out special operations until the statute of limitations expires in October.

Under South Korean law, a fine of more than 1 million won ($863) handed down to lawmakers-elect results in the invalidation of their elections.

During the 2012 general polls, authorities indicted 30 lawmakers-elect until the statute of limitations expired, leading to invalidation of 10 candidates' elections, according to the SPO. (Yonhap)