A major South Korean labor umbrella group staged a one-day nationwide strike Wednesday to oppose political parties' move to expand a flexible work hour system. 

The Korean Confederation of Trade Unions said about 130-thousand affiliated unionized workers will join the walkout across the nation. The labor group also held a massive rally in front of the National Assembly at 3 p.m.

The group opposes rival parties' move to revise the new 52-hour workweek system to allow a more flexible operation of the scheme in consideration of businesses.

The labor unions said the revised system could hamper workers' health and offset the effect of reduced working hours.

The KCTU has refused to join a new multilateral committee seeking social dialogue that involves representatives from the labor, management and the government.