SEOUL (BLOOMBERG) - A powerful storm that lashed South Korea's southern coast earlier this week has left one of the country's biggest steelworks shuttered, spurring concerns over the nation's production.

Posco, the country's biggest steel-maker, as well as Hyundai Steel Co, suspended operations at their plants in Pohang after Super Typhoon Hinnamnor flooded facilities there, according to regulatory filings on Wednesday (Sept 7).

Posco's Pohang works is one of its two main sites in South Korea, and hosts a significant portion of the group's 40 million tonnes of annual crude steel capacity.

Three of Posco's blast furnaces will restart as soon as power is restored, though the firm is still reviewing the resumption date for the plant as a whole, it said in the filing.

Hyundai Steel said the suspension won't hurt its profit because the company can ramp up production at two other locations in Incheon and Dangjin.

Posco views the power outage as a force majeure event, and plans to restart a flooded power substation in one or two days, according to a statement on Wednesday.

The Pohang-based company will increase production at its Gwangyang steelworks as much as possible, the statement said.

Hyundai Steel closed down 0.2 per cent in Seoul, while Posco Holdings Inc slumped 2.6 per cent.

The benchmark Kospi fell 1.4%.

The typhoon that battered South Korea early on Tuesday left at least six people dead and created flooding and power outages.

Most businesses, schools and public transport in the country returned to normal soon after the storm had passed.