"We are short units of Icahn Enterprises and have initiated a short position in IEP bonds," the research report said, sending the shares of the investment firm down 6.1% in premarket trading.

Last week, Hindenburg accused the investment firm of overvaluing its holdings and operating a "Ponzi-like" structure to pay dividends. Icahn has called the report "self-serving" and vowed to fight back.

Hindenburg said Icahn's latest disclosures raise critical new questions about margin loans and continued portfolio losses.

(Reporting by Jaiveer Singh Shekhawat in Bengaluru; Editing by Arun Koyyur)