Workers at South Korea's two largest automakers went on a limited strike Friday to press their demands for wage reforms, their unions said.
Unionists at Hyundai Motor Co. and its subsidiary Kia Motors Corp. downed tools for four hours.
They have held 17 rounds of talks with the management over the past two months but have been unable to reach a compromise, a Hyundai Motor union spokesman said.
"Negotiations stalled on whether to count regular bonuses towards ordinary wages," he said.
This would increase workers' incomes by an average 10 percent by increasing overtime pay, he added.
The union said its workers would also refuse to work overtime this weekend.
Yonhap news agency said the strike would cost Hyundai-Kia Motor Group a total of some $64 million in lost production.
The Hyundai Motor union voted for the strike on August 14, with 70 percent of 47,262 union members voting in favour of industrial action.
The Supreme Court ruled in December last year that bonuses paid regularly should be considered as part of ordinary wages.
The ordinary wages are used as the basis for setting allowances such as overtime pay, holiday shift pay and paid annual leave, as well as pension, according to the law.