The main opposition party's filibuster, designed to block a ruling party-led bill on electoral reform, ended at the stroke of midnight Wednesday night, as the extra parliamentary session came to a conclusion.

The contentious bill will be put to a vote during the new extra session at the National Assembly, which will convene at 2 p.m. Thursday and end on Sunday.

Joo Ho-young, a four-term lawmaker of the main opposition Liberty Korea Party, began to filibuster at 9:49 p.m. on Monday, soon after Speaker Moon Hee-sang introduced the electoral reform bill for a parliamentary vote.

Earlier that day, the ruling Democratic Party, three minor parties -- the minor conservative Bareunmirae Party, the liberal Party for Democracy and Peace and the progressive Justice Party -- and one splinter group reached a final agreement on the details of bills on new parliamentary election rules and overhauling the prosecution, following weeks of intense negotiations.

This was the first filibuster at the National Assembly in nearly four years.

Joo got the ball rolling for the LKP by going one minute shy of four hours. But members of the DP and other parties took the podium too and voiced their support of the electoral reform bill.

Lawmakers spoke for anywhere between 45 minutes and five hours and 50 minutes over the past three days.

In April, the DP and the three small parties put the bills on a parliamentary fast-track, drawing the ire of the LKP.

A key bone of contention was how to introduce a mixed-member proportional representation system ahead of the April 15 general elections.

Under the deal, the number of directly elected seats and proportional representation slots will be kept at 253 and 47, respectively, in the 300-member National Assembly.

The number of PR posts to be allocated under the MMP representation scheme will be capped at 30.

The existing single-member district system is credited with advancing South Korea's democracy. But it has also generated many dead votes and has mostly benefited the two large parties, in turn worsening deeply-rooted regionalism.

Under MMP, parliamentary seats are tied to the percentage of voters' support for political parties.

Smaller parties voiced support for introducing the new PR system to increase their presence in the parliament.

Monday's deal backpedaled from a tentative agreement reached between the DP and the three minor parties in April, under which the number of PR slots would have been raised to 75. It also scaled back the parties' attempt to raise the number of PR seats to 50.

For the DP, it is politically burdensome to push for electoral reform without the participation of the LKP. But the governing party appears to have set a goal of cementing cooperation with minor parties.

The LKP called its rivals' agreement political collusion, vowing to deter the parliamentary passage of the measures. (Yonhap)