South Korean companies suffered a further setback last year following a sluggish 2014, with manufacturers grappling with sales reductions amid the global economic slowdown, a report showed Friday.

Sales by 19,638 companies whose assets were valued over 12 billion won ($10.1 million) slipped 2.4 percent in 2015 compared with a year ago, the Bank of Korea said in a 2015 report on corporate management.

Revenue from manufacturers, the nation's main growth driver, fell 4.2 percent on-year due to a slowdown in the Chinese economy and faltering demand from the Middle East in the wake of cheap oil prices.

By sector, the petrochemical industry marked the highest sales drop of 16.8 percent. Electricity and gas fell 11.9 percent and metal products decreased 7.3 percent.

Sales from large enterprises retreated 3.8 percent on-year, but the corresponding figure for small and mid-sized companies rose 4.2 percent, the report said.

The operating margin improved thanks to cheaper fuel costs, rising from 4.3 percent in 2014 to 5.2 percent in 2015.

"The favorable foreign exchange rate and a drop in raw material costs, including crude oil, boosted corporate profitability," BOK official Park Sung-bin said.

The average won-dollar exchange rate was at 1,131.5 won in 2015, down 7.4 percent from a year earlier.

Refiners were the biggest beneficiary of the weaker local currency, which drove up their operating margin from 2.7 percent to 6.8 percent during the period.

In contrast, shipbuilders' profitability shed 0.4 percentage points to 1.7 percent as local companies were carrying out restructuring to tackle a protracted industry slump.

The average debt ratio among the companies fell from 106.5 percent in 2014 to 100.9 percent in 2015 as major firms made belt-tightening adjustments under the tough business conditions.

"It seems that companies repaid debt with cash income, while depositing some money in their reserves," Park said. (Yonhap)