India's Adani says US charges 'baseless', opposition demand arrest

India's Adani Group on Thursday called US charges that their billionaire tycoon founder Gautam Adani had paid more than $250 million in bribes "baseless", as the opposition leader demanded his arrest.

The stiff denial came after shares in the industrialist's conglomerate nosedived more than 23 percent in Mumbai, the morning after a bombshell indictment in New York accused him of deliberately misleading international investors.

Adani, once the world's second-richest man, is a close ally of Hindu nationalist Prime Minister Narendra Modi and critics have long accused him of improperly benefitting from their relationship.

"The allegations made by the US Department of Justice and the US Securities and Exchange Commission against directors of Adani Green are baseless and denied," the conglomerate said in a statement.

"All possible legal recourse will be sought," it added.

But Congress party leader Rahul Gandhi said the businessmen should be taken into custody.

"We demand that Adani be immediately arrested. But we know that won't happen as Modi is protecting him," Gandhi told reporters in New Delhi.

"Modi can't act even if he wants to, because he is controlled by Adani."

Wednesday's indictment accuses Adani and multiple subordinates of paying huge sums of more than $250 million in bribes to Indian officials for lucrative solar energy supply contracts.

The deals were projected to generate more than $2 billion in profits after tax over roughly 20 years.

None of the multiple defendants named in the case are in custody.