Kia Motors Corp., South Korea's second-biggest automaker, said Thursday that it has reached a tentative wage deal with its union after days of partial strikes.

The agreement reached early Thursday 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 two sides also agreed to double the amount of social contribution to 2 billion won to support the underprivileged in society, according to the company.

The company said about 30,000 union members are set to vote on the tentative agreement on Friday, adding that the deal could be concluded if at least half vote in favor.

The tentative deal came weeks after Kia's 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 two days after the union of Kia's bigger sister company Hyundai Motor Co. voted to accept 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)