The main opposition People Power Party (PPP) claimed four of the five National Assembly seats up for grabs in by-elections, putting the icing on the cake in its victory during a tightly fought presidential race.

The by-election result will increase the conservative PPP's presence at the National Assembly to 110 seats, though the number is still far behind the ruling Democratic Party (DP)'s 172 seats in the 300-member National Assembly

The PPP's first win came in Anseong, south of Seoul, where veteran politician Kim Hack-yong confirmed his return to the National Assembly. Kim garnered about 54 percent of the vote and beat two other candidates.

Another PPP candidate Chung Woo-taik then won in the central city of Cheongju after getting nearly 57 percent of the vote.

Choe Jae-hyeong, former chief of the national audit agency, was the next PPP winner after collecting 52.1 percent of the vote in Seoul's Jongno district.

PPP's Cho Eun-hee was the last one to join them as she won Seoul's Seocho district with more than 70 percent of the vote.

Meanwhile, independent candidate Lim Byung-heon won the seat in the southeastern city of Daegu after collecting 22.4 percent of the vote. (Yonhap)