The union of South Korea's second-largest automaker Kia Motors Corp. said Friday that its members have voted in favor of a tentative wage deal reached earlier this week.

The deal calls for a hike of 97,000 won ($89) in basic salaries and 8.5 million won in incentive payments and performance-related bonuses as well as other benefits.

The carmaker said it has agreed to double the amount of social contribution to 2 billion won to support the underprivileged in society.

The endorsement came weeks after about 30,000 unionized workers staged days of partial strikes that prevented Kia from producing 23,271 units, costing the carmaker 413.5 billion won in lost production.

It also came three days after the union of Kia's bigger sister company Hyundai Motor Co. approved a similar wage deal.

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

Labor disputes at Hyundai Motor have been an almost annual event over the past two decades. Its workers have downed tools every year since 1986 except in 1994, 2009, 2010 and 2011.

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. (Yonhap News)