Trading in the business empire of Asia's richest man Gautam Adani was halted on Friday following a 15 percent plunge in its share price, days after a US investment firm claimed it had committed "brazen" corporate fraud.

Flagship Adani Enterprises tumbled to 508.45 rupees (US$6.23) in Mumbai in the afternoon, triggering an automatic 105-minute trading halt, while subsidiary Adani Total Gas also halted after it tanked 20 percent.

Hindenburg Research this week alleged in a report that Adani Group had used undisclosed related-party transactions and earnings manipulation to "maintain the appearance of financial health and solvency" of its listed business units.

Adani, 60, was the world's third-richest person on Wednesday, but on Friday fell to seventh place on Forbes' billionaires tracker after losing US$19 billion when trading resumed in India following a Republic Day holiday.

Adani's sprawling interests range from Australian coal mines to India's biggest ports and the combined market cap of its seven listed companies exceeded US$218 billion at the start of the week.

The conglomerate said on Thursday it was the victim of a "maliciously mischievous" reputational attack by Hindenburg just as it was preparing for a major fundraising round.

Adani's legal chief, Jatin Jalundhwala, said in a statement that Hindenburg's short-sell position in the firm, announced in the report's release, was proof the company had a vested interest in driving down Adani stocks.

Adani was exploring its punitive action against the research advisory in US and Indian courts, he added.

Hindenburg responded that Adani had ducked the issues its research had raised and instead resorted to "bluster and threats".

"If Adani is serious, it should also file suit in the US," the firm said in a statement. "We have a long list of documents we would demand in a legal discovery process."

Shares in Adani business units have soared as much as 2,000 percent in the past three years, adding more than US$100 billion to its founder's net worth and vaulting him up the ranks of the world's richest people. (AFP)