SEOUL, South Korea: unioized workers at Hyundai Motor Co., South Koreas largest automaker, resumed a walkout on Aug. 8 after failing to hammer out a wage deal with management.

Some 45,000 unioized workers went on a two-hour strike earlier in the day after asking Hyundai management to increase salary and to end night shifts that workers say are a health hazard.

The labour unio said Hyundai employees will halt work for several hours on six days between Aug. 8 and Aug. 17 and will refuse overtime work on those days.

Workers at factories in Ulsan, Asan and Jeonju joined the strike.

The strike comes amid growing frictions between workers and management in South Koreas auto industry.

Hyundais smaller affiliate, Kia Motors Corp., plans to join the strike later this week in a bid to mount pressure on management in wage negotiations.

Separately, workers at GM Korea, South Koreas third-largest carmaker and the unit of General Motors Co., also plan to strike.

Hyundai Motor reported a record quarterly profit in the April-June quarter thanks to strong overseas sales that masked a sales slump in South Korea. But South Korean automakers face heightened competition from Japanese rivals that have been rebounding from a devastating earthquake in 2011.

Hyundai Motor issued a statement denouncing the labour strike.

It is regrettable that the labour unio has decided to go on strike and interrupt negotiations at this critical point. The unio walkout is counterproductive and will harm the workers and Hyundai customers, as well as the company, the statement said.

In July, workers at Hyundai and Kia staged their first walkout in at least three years. Company representatives said the July strikes reduced output by 14,080 vehicles worth 269.4 billion won ($239 million) at the two automakers.

Hyundai Motor is the crown jewel of the Hyundai Motor Group, the worlds fifth-largest automotive group, which has Kia Motors under its wing.