Unionized workers of South Korea's second-largest carmaker Kia Motors Corp. went on a partial strike Thursday to press their demand for a wage hike and other fringe benefits, a company official said.

The walkout by about 30,000 workers, the second since last Wednesday, comes a day after their leaders failed to work out differences with their management in the latest negotiations. The workers also plan to down tools for four hours on Friday.

The union calls for, among other things, a special bonus amounting to 30 percent of the company's net profit last year, which reached 3.8 trillion won (US$3.4 billion).

The union is also asking for a hike of 130,000 won in basic pay and a gradual extension of the retirement age up to 65, as well as free breakfast and dinner, according to the company official.

The official said the carmaker's management would make a counterproposal for a hike in basic salary, and other compensation demands on Friday.

Kia's union officials were not immediately reached for comment.

The latest work stoppage comes as union leaders of Kia's bigger sister company Hyundai Motor Co. opened a fresh round of negotiations with management over a similar pay hike and other fringe benefits.

On Wednesday, Hyundai's 46,000 unionized workers walked off the job for eight hours, the fifth since last Tuesday.

Hyundai and Kia, which together form the world's fifth-largest automaker, have long been plagued by labor disputes.

Hyundai's workers have downed their tools every year since 1986 except for 1994, 2009, 2010 and 2011. A strike last year cost the carmaker some 1.7 trillion won in lost production.

Kia's union has gone on strike every year except in 2010 and

2011 since 1999, when the country's No. 2 carmaker was taken over by Hyundai following the 1997-98 Asian financial crisis.

Despite the latest labor disputes, Hyundai and Kia performed well in China, the world's largest auto market.

Hyundai and Kia said their cumulative sales in China surpassed the 1 million mark in the first eight months of this year, the fastest pace in four years. In 2010, the two carmakers hit the 1 million sales milestone in the third week of December.

(Yonhap News)