Early voting for the July 30 parliamentary by-elections kicked off Friday for a two-day run amid expectations the vote will serve as a referendum on President Park Geun-hye's conservative administration.

The polls carry extra weight this year because a total of 15 parliamentary seats are up for grabs, the largest-ever number for a by-election. They also come less than two months after the June 4 local elections in which neither the ruling nor the main opposition party claimed a clear-cut victory.

Early voting began at 257 polling stations in the 15 constituencies nationwide at 6 a.m. Voting will take place between 6 a.m. and 6 p.m. on both Friday and Saturday.

The ruling Saenuri Party has vowed to reclaim an absolute majority in the 300-member National Assembly, where it currently holds 147 out of 285 seats.

The main opposition New Politics Alliance for Democracy (NPAD), meanwhile, has called for judgment on the Park administration, saying the government failed the people in its poor response to April's ferry sinking that claimed the lives of more than 300 people, mostly high school students.

On the eve of the early voting period, three opposition candidates withdrew from their respective races in a move seen as boosting the opposition bloc's chance of victory.

Gi Dong-min of NPAD withdrew from Seoul's Dongjak-B constituency to support Roh Hoe-chan of the minor opposition Justice Party. The merger came as Na Kyung-won of the ruling party was seen as having a clear lead over the two.

Cheon Ho-sun, the chief of the Justice Party, also quit the race for a seat in Suwon, just south of Seoul, to back Park Kwang-on of the NPAD, while the Justice Party's Lee Jeong-mi withdrew from another district in Suwon, leaving NPAD's Sohn Hak-kyu as the main opposition candidate in that election. (Yonhap)