• "After extensive research, we have taken a short position in Adani Group Companies through U.S.-traded bonds and non-Indian-traded derivative instruments," Hindenburg announced in its report.
• Shares of Adani-affiliated companies fell after the short seller firm accused the conglomerate of corporate fraud.
• Adani Group called Hindenburg's report "malicious combination of selective misinformation," in an emailed statement to CNBC.

Short seller firm Hindenburg announced its short position in Adani Group companies ahead of India's market open on Wednesday and accused billionaire Gautam Adani of engaging in "brazen" stock manipulation and accounting fraud.

"After extensive research, we have taken a short position in Adani Group Companies through U.S.-traded bonds and non-Indian-traded derivative instruments," Hindenburg announced in a lengthy report published on its website.

NEW FROM US:

Adani Group – How The World’s 3rd Richest Man Is Pulling The Largest Con In Corporate Historyhttps://t.co/JkZFt60V7f

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— Hindenburg Research (@HindenburgRes) January 25, 2023

"Today we reveal the findings of our 2-year investigation, presenting evidence that the INR 17.8 trillion (U.S. $218 billion) Indian conglomerate Adani Group has engaged in a brazen stock manipulation and accounting fraud scheme over the course of decades," Hindenburg said in its report.

Adani-affiliated stocks fell, with Adani Port closing 6.31% lower on Wednesday. Adani Power's share price fell 4.97%, Adani Transmission lost 8.85% while Adani Enterprises shed 1.54%.

Adani Group called Hindenburg's report a "malicious combination of selective misinformation," adding that it has "always been in compliance with all laws."

"The timing of the report's publication clearly betrays a brazen, mala fide intention to undermine the Adani Group's reputation," the group's chief financial office Jugeshinder Singh said in an emailed statement to CNBC.

The group also said Hindenburg published its report "without making any attempt to contact us or verify the factual matrix."

Hindenburg also alleged the Securities and Exchange Board of India was lax in its investigation of Adani's offshore funds as well as enforcement of regulations that would have subject Adani companies to delisting. The SEBI did not immediately respond to CNBC's request for comment.

Since becoming a billionaire in 2008, Adani is now one of the richest people in the world with a $119 billion fortune, according to the Bloomberg Billionaires Index.

In August, the company sought a hostile takeover of Indian media group NDTV, which in a filing said the move was "carried out without any consent" from its founders.

— CNBC's Naman Tandon contributed to this report.