South Korean companies with weak financial footing saw their balance sheets worsen further this year amid a protracted economic slowdown, with their debt ratio sharply rising and their ability to pay back interest declining, industry data showed on Sunday.

According to the data, the top 300 in terms of debt ratio, out of 1,501 listed non-financial firms, had the average debt ratio of 279.2 percent as of end-June this year, rising 35.7 percentage points from a year earlier.

The June figure also compares with 259.3 percent at the end of June 2009, when the collapse of Lehman Brothers sent a shock to the global economy, the data showed.

The data showed that their interest coverage ratio reached 425.8 on average as of end-June, improving from 292.8 percent at the end of June 2009.

But their interest-paying capability further declined when Samsung Electronics Co., Hyundai Motor Co. and three other major firms were excluded from the calculation, with their interest coverage ratio standing at 245 percent, according to the data.

The ratio, or a firm's operating profit divided by its interest costs, measures the company's ability to pay interest on outstanding debt.

Analysts said the financially vulnerable firms may further face difficulty down the road, as economic recovery is still delayed, and an early tapering of the U.S. Federal Reserve's massive stimulus is widely expected to further hit the shaky players.

Already, some business groups such as Hanjin and Dongbu are showing signs of reeling from liquidity shortages even after leading conglomerates such as STX Group and Tong Yang Group are forced to conduct massive restructuring steps, such as assets sales. (Yonhap news)