Union workers at Kia Motors resumed their partial strike on Monday, the first walkout since the union rejected a tentative wage deal late last month, a company official said.

Kia's 28,000-strong union staged a four-hour work stoppage during the day, with the official saying it would cost 13.8bn won ($14.8m) in lost production, according to a Yonhap news agency report on Asia Pulse.

The union on 27 July voted against the deal for a 5.2% increase in basic salary and a bonus equivalent to one-and-a-half months of salary.

Including Monday's production loss, Kia estimated partial strikes would force it to have lost production worth 377.1bn won so far this year, the anonymous official said.

The report noted the union had originally demanded an 8.9% rise in basic salary and a bonus equivalent to two months' salary.