One of South Korea's two major umbrella unions launched a sit-in at the Democratic Party(DP) headquarters, demanding passage of the so-called "yellow envelope bill" aimed at limiting the ability of companies to seek compensation against unions for losses incurred during strikes.

On Monday, members of the Korean Confederation of Trade Unions(KCTU), who have been staging a hunger strike in front of the National Assembly, reportedly entered the party headquarters at around 8 a.m.

The union members are urging the DP to push for the bill's passage within the year and demanding talks with party leader Lee Jae-myung.

A union representative accused the main opposition of backtracking on its earlier pledge to include union law revisions in its package of livelihood bills and emphasized that the DP must responsibly handle the revision bill at the parliamentary standing committee this week.