"It appears that there was a problem in the switchgear of the Yeongseo Substation," KEPCO said, adding a probe is still under way to determine the exact cause.

The company said it restored most of the power by around 1:15 p.m. by drawing on electricity from the Shinyangjae Substation instead.

Cho Hwan-eik, head of KEPCO, offered a public apology.

"All responsibility for the blackout lies with KEPCO, and I extend my deepest apologies to citizens who suffered tremendous inconveniences while enjoying rest and leisure on a Sunday," he said in a statement. "We will do our best to prevent a recurrence by carrying out a thorough investigation of malfunctions in equipment."

The company will continue to monitor the damage caused by the blackout and swiftly compensate those who were affected, he added. 

It is estimated that some 190,000 households were affected by the latest power failure, according to KEPCO.

Firefighters said that there were scores of calls by citizens trapped in elevators, including a case involving a Techno Mart store, a shopping mall for electronics goods in Seoul's southwestern area.

In another instance, people rushed to escape from a building affected by a blackout while a wedding ceremony was underway, according to witnesses.

Later in the day a similar blackout occurred in Daegu, 302 kilometers southeast of Seoul.

According to KEPCO, power was cut off around 5:16 p.m. from seven neighborhoods and restored 16 minutes later.

More than 3,700 households are estimated to have been affected, with two cases of people being trapped inside elevators, it said. An examination is underway to determine the exact cause. (Yonhap)