Thousands of unionized workers of Hyundai Steel Co. began a walkout Wednesday to demand higher wages and bonuses amid the COVID-19 pandemic, the union said.

The workers will go on strike for two days through Thursday, affecting production at five domestic plants of South Korea's second-largest steelmaker, the union said.

Still, some 2,000 essential workers did not join the strike as they need to work at three blast furnaces in Dangjin, about 120 kilometers south of Seoul.

The strike by the 8,400-strong union came after the company and the union failed to narrow differences over wages and bonuses in 15 rounds of negotiations.

The union demanded an increase of 120,000 won ($109) per person in basic monthly pay, a bonus amounting to three months of salary and 5 million won in special allowance.

But the company proposed a freeze on basic pay, a bonus amounting to one month of salary and 1 million won in special allowance.

In 2019, Hyundai Steel, the steelmaking unit of Hyundai Motor Group, staged a strike. (Yonhap)