The parliamentary and local by-elections were conducted in 12 districts across the country. Three National Assembly seats, two chief local administration posts and seven local assembly slots were at stake.

Overall voter turnout came in at 33.5 percent, slightly higher than the average 32.4 percent recorded in previous by-elections.

The results increased the majority Saenuri Party's parliamentary seats to 154, compared with the main opposition Democratic United Party’s 127.

Ahn, a liberal politician, had 60.5 percent of the vote in Seoul’s Nowon-C constituency. The figure for his closest rival, Huh Joon-young of the Saenuri Party, stood at 32.8 percent.

“I thank the Nowon residents and the public who supported me. I will repay with good politics. (Nowon) residents and members of the public, please watch my new start,” Ahn said. 

Ahn, however, declined to comment on his future plans.

“I think parliamentary activities need preparations, and (conducting them) needs time. I will announce my future plans after these things have been taken care of to a certain extent.”

Ahn taking the National Assembly seat left vacant by Roh Hoe-chan of the minor opposition Progressive Justice Party is expected to set off a major shake up in the progressive bloc, dominated by the DUP.

Observers say that Ahn may either join the DUP or establish his own party.

According to a survey by Gallup Korea in the first week of March, a new party headed by Ahn would gain 23 percent support, while the DUP would fall to 11 percent.

The survey also showed that about 38 percent of current DUP supporters would move over to Ahn’s party.

The two Saenuri politicians also cruised to victories in their respective constituencies.

Kim is an experienced politician who served four terms in the National Assembly and is a key ally of President Park.

“I will take the calls to bring about the advancement of Yeongdo (Busan) and to help the Park Geun-hye government succeed to heart, and I will do my part as soon as entering the National Assembly,” Kim said.

He won 65.7 percent of the vote, against 22.3 percent earned by his rival Kim Bi-oh from the DUP.

He is a former ruling party floor leader and was the campaign chief for Park during last year’s election.

He has been widely speculated to run for the Saenuri Party leadership. He denied the rumors saying that the leadership’s tenure needed to be guaranteed.

Lee had a sweeping victory in the Buyeo-Cheongyang constituency in South Chungcheong Province, where he formerly served as governor.

Lee had received 77.4 percent, defeating Hwang In-seok from the DUP who won 16.9 percent.

Voter turnout for the three parliamentary constituencies stood above the national average.

At the end of voting, 43.5 percent of Nowon-C voters had cast their ballots, while 36 percent of Yeongdo residents had voted. The figure for the South Chungcheong constituency stood at 44.2 percent.

The elections were held at 283 polling stations across the country from 6:00 a.m. to 8 p.m.

By Choi He-suk (cheesuk@heraldcorp.com)