SEOUL, Dec. 9 (Yonhap) -- Affiliates of Doosan Group, a machinery and construction equipment conglomerate, saw their credit ratings downgraded by local rating appraisers due to lingering concerns over their financial health despite the market debut of a key affiliate, industry sources said Friday.

Doosan Bobcat Inc., a unit of the country's leading construction equipment maker Doosan Infracore, raised some 900 billion won (US$773 million) through the IPO last month, the second-largest IPO deal after Samsung BioLogics Co.'s 2.2 trillion-won market debut early this month.

Originally, Doosan Bobcat, a leading player in the small construction machinery sector in the United States, had sought to raise as much as 2.45 trillion won but cut its IPO deal due to lukewarm responses from investors.

Doosan Infracore and Doosan Engine Co. own a majority stake in Doosan Bobcat. In particular, Doosan Infracore holds 59 percent in Doosan Bobcat.

Korea Investors Service Inc., a rating agency, cut its rating on Doosan Infracore to "BBB-" from "BBB," citing the company's burden of paying off heavy debts amid weaker-than-expected cash flow from Doosan Bobcat's market listing.

"Some 240 billion won worth of liquidity has been funneled into Doosan Infracore, which is smaller than expected," the rating agency said. "The company is still saddled with a heavy debt payment burden, and its liquidity level is heavily dependent on Doosan Bobcat's stock price."

The IPO was part of Doosan Group's efforts to improve its financial status. The power-to-construction equipment conglomerate has raised trillions of won by selling assets in recent years to survive a prolonged slump in the construction industry.

KIS Ratings also lowered its rating outlook for Doosan Corp. and Doosan Heavy Industries & Construction Co. to "negative" from "review for rating downgrade."

NICE Investors Service Inc. also lowered its rating outlook for key affiliates, such as Doosan and Doosan Infracore, citing the lack of much improvement in their financial health following Doosan Bobcat's IPO.

"After the Doosan Bobcat's IPO, what is important for now is how to reduce the financial burden held by Doosan Infracore and Doosan Engine," said Park Se-young, an analyst at NICE Investors Service. "We need to closely monitor each affiliate's business performance."

As of end-June, Doosan Infracore's debt stood around 2.3 trillion won, with about 1.5 trillion-won debt maturing within one year.

Some analysts raised the possibility that Doosan Infracore may take out loans with its stake in Doosan Bobcat as collateral.

Hit by a protracted slump in the construction sector, Doosan Infracore logged a loss of 859 billion won last year, with its operating income dropping 94 percent on-year to 27.4 billion won.