A combined 110,000 workers at Hyundai Motor and smaller car makers, textile companies, department stores and other workplaces are due to lay down tools on Tuesday, according to Reuters.

The Korean Confederation of Trade Unions, which has 600,000 members and is the country's second-largest labour group, has threatened to unleash a summer of labour discontent, demanding higher wages and better working conditions, the report said.

The KCTU reportedly has also vowed to protest against sending more troops to Iraq after the killing of a South Korean hostage by Muslim militants last week - the labour minister has urged unions not to link strikes to the deployment.

"We will go ahead with the planned strike unless there is a breakthrough in talks with the government and management on our demands, including action plans for a five-day work week," KCTU spokesman Kang Chul-Ung said, according to Reuters.

Wage negotiations between Hyundai's management and its 40,000-strong union have unravelled, the report noted.

Seeking a 10.48% increase in wages and a hefty bonus, Hyundai's union reportedly held a second six-hour strike on Monday after similar action on Friday and a full strike is slated for Tuesday and Wednesday.

Unionised workers at affiliate Kia Motors will strike for eight hours on Tuesday, while smaller rival Ssangyong Motor Co. will hold a four-hour strike, the report added.

The Federation of Korean Trade Unions, which is the country's largest labour group and encompasses 36 financial institutions and state agencies, said it was preparing for a general strike, led by the financial sector unions in mid-July, Reuters noted.