Early voting for next week's by-elections kicked off Friday, with a handful of parliamentary candidates casting their ballots in a bid to draw voters to the polls.

The early voting system is different from absentee voting in that it does not require voters to sign up in advance. Voters who expect to be busy or away on the election day can simply show up at a polling station during the voting period and cast their ballots.

Early voting will run until Saturday.

It is the first time for the new system to be tested after it was introduced under a revised law in February 2012.

A total of three parliamentary seats are being contested in the April 24 by-elections, including one in Seoul and another in the southeastern port city of Busan.

The remaining seat is for the Buyeo and Cheongyang constituency in South Chungcheong Province.

The elections initially drew public and media attention due to former presidential candidate Ahn Cheol-soo's bid for Seoul's Nowon C district.

However, the recent security tensions on the Korean Peninsula sapped away most interest in the races, leading all opposition candidates and the independent, Ahn, to cast their votes on Friday as a way to drum up support for their bids.

Ahn's rival Huh Joon-young of the ruling Saenuri Party is still scheduled to vote on the main election day, along with Saenuri candidate Lee One-koo, a former governor of South Chungcheong Province, who is running for the seat in Buyeo and Cheongyang.

In Busan, ruling party candidate Kim Moo-sung, a former Saenuri floor leader and close aide to President Park Geun-hye, cast his ballot earlier in the day.

Ahn, Lee and Kim have all been the front-runners in their respective constituencies, according to public opinion surveys. (Yonhap News)