South Korea asked North Korea on Tuesday to extend a deadline by which Seoul firms should pay wages to their workers at a joint industrial complex in the North, a government official said.

Three of the 124 South Korean firms have paid the March wages to North Korean workers at the Gaeseong Industrial Complex in the North's border town of the same name amid a drawn-out wage row among the two Koreas.

In February, the North unilaterally decided to raise the minimum monthly wage by 5.18 percent to $74 starting in March for about 53,000 North Korean workers at the complex.

Seoul has not accepted the North's unilateral move, saying that Pyongyang violated a 2004 agreement that calls for the two sides to set the wages together. The wage cap has been set at 5 percent per year. Seoul warned that violators would be penalized.

Despite Seoul's warning, three unidentified South Korean firms paid the wages on Monday, the original deadline, and signed documents that guaranteed their duty to pay arrears.

An official at Seoul's unification ministry said that it has asked the North to delay the deadline through quasi-government committees.

"The government made a written request to the North over the deadline extension," said an official, asking not to be named. "We have not yet received a response from the North."

After making a one-day visit to the industrial park, officials from the Seoul firms said Monday that Pyongyang decided to extend the deadline by a week for the March wage payment.

It is not immediately known whether or how long the North will officially delay it.

Meanwhile, Seoul's unification ministry said Tuesday it is first looking into why the three firms paid the wages before deciding whether to impose punitive actions against them.

"The three firms followed the government's guidance that they should stick to the current wage agreement," an official said, asking not to be named. "But we think that it is problematic that North Korea required them to make pledges to pay arrears later."

The North has threatened to collect arrears from the South Korean firms if they do not pay the higher wages.

South Korea is concerned that the wage row could set a precedent for the North to make unilateral decisions on the operation of the industrial park.

The Gaeseong Industrial Complex opened in the early 2000s and is the last remaining symbol of inter-Korean reconciliation. It has served as a major revenue source for the cash-strapped communist North, while South Korea has utilized cheap but skilled North Korean laborers. (Yonhap)