Shares in the main listed unit of Indian billionaire Gautam Adani's conglomerate fell 25 percent on Tuesday as an ongoing vote count in national elections suggested a reduced majority for Prime Minister Narendra Modi's party.

Adani is considered a longtime close associate of Hindu-nationalist Modi, both from Gujarat state.

Opposition parties and other critics have accused Adani of benefitting from their relationship to unfairly win business and avoid proper oversight.

Adani Enterprises was trading at $32.72 (2,733 rupees) per share after midday, down $9.05 from Tuesday's open.

It was the biggest negative mover on the Mumbai stock exchange, with the Sensex benchmark falling more than seven percent by afternoon trade.

Exit polls had predicted a landslide victory for Modi's Bharatiya Janata Party (BJP) and its allies in this year's election.

With nearly half of the vote counted, election commission figures on Tuesday afternoon still showed Modi on course to win a third term but with a reduced majority.