A series of strikes have hit the South Korean motor industry, as workers demanded higher wages and a say in whether plants move overseas.
Strikes are expected to be short-lived this year
Some 40,000 workers at Hyundai Motor staged a protest on Tuesday while staff at its affiliate Kia Motors Corp staged a walk out.
Ssangyong Motor suffered a four-hour morning shutdown.
A rise in salaries would threaten South Korea's competitive edge over Japanese and US car makers.
The government is already battling to improve lacklustre domestic demand and business spending.
At Hyundai, employees are demanding a 10% pay increase and a bonus of 30% of profits.
Strikers have also said they will protest at the sending of more troops to Iraq following the execution last week of a South Korean hostage.
Staff at Kia are demanding a similar wage hike and an increase in bonuses.
As well as wage rises, Ssangyong's union wants the management to seek its approval before moving plants overseas.
South Korea usually sees increased strike action in summer.
Mark Yoon, an analyst at Merrill Lynch, said he did not expect this year's labour disputes to be as violent or disruptive as those of last year.
Action at Hyundai last year went on for about 45 days.