South Korea said Wednesday it will ask the country's firms at the Gaesong Industrial Complex in writing not to succumb to North Korea's pressure to raise wages for its workers.

The unification ministry said it will soon send a formal letter to 124 South Korean firms operating in the zone just north of the inter-Korean border.

The move comes as the companies, mostly small and medium-sized, will begin to pay March's wages to around 53,000 North Korean employees on April 10.

In February, the North decided unilaterally to revise a set of labor rules that included the elevation of the minimum wage for its workers at the Gaesong Industrial Complex from $70.35 to $74 starting in March.

The South has rejected the North's decision, saying the wage issue should be decided through bilateral discussions.

It has urged the South's firms in Gaesong not to follow the North's measure.

"We plan to send an official letter to them in order to again make clear the government's stance on the matter," Unification Ministry spokesman Lim Byeong-cheol said.

He added there has been no progress yet in efforts to hold talks with North Korea to discuss the issue. (Yonhap)