South Korea's major petrochemicals firms are increasingly tapping the local bond market to capitalize on low rates and an improvement in their bottom lines, industry sources said Sunday.

According to the sources, Kumho Petrochemical Co. is planning to sell 70 billion won ($62.5 million) worth of debts next month following the 45 billion-won debt sale in March to refinance 100 billion won worth of debts that mature in July.

The maturing debt carries a coupon rate of 4.7 percent, but next month's debt is expected to be priced at a rate of 3.4 percent, the sources said.

Hanwha Chemical Co. also sold debt worth 100 billion won earlier this week, larger than the originally proposed 50 billion won, in response to strong demand.

The chemical company said the proceeds from the debt sale will be used to pay for raw materials and refinance maturing debt, it said in a regulatory filing.

It reported a 38 percent rise in its first quarter operating income at 197 billion won.

Last week, LG Chem Ltd., South Korea's top chemicals firm, floated 800 billion won worth of debt to fund the expansion of its facility and refinance short-term maturing debt.

LG Chem had originally planned to sell 500 billion won worth of debt but jacked up the amount issued in the face of strong demand.

The bond issue is the largest for the company since 2012.

LG Chem, racked up an operating income of 797 billion won in the first quarter, up 74.1 percent from a year earlier, marking the highest in six years.

In a book building process for institutional investors, orders for the debt sale amounted to a total of 1.77 trillion won, LG Chem said earlier.

The company said proceeds from the debt sale will be used to finance facility expansion. (Yonhap)