Two more rounds remain to be completed in the world's largest democracy before May 10 for the 545-member lower house of parliament with more than 650 million eligible to vote. Results will be declared May 13.
Previous opinion and exit polls had predicted the ruling coalition led by the BJP party would win a big majority because of the unprecedented economic growth in a country of more than 1 billion population.
However, one exit poll conducted by Aaj Tak TV after Monday's balloting for 136 seats gave the BJP a bare majority or even less, the Times of India reported.
BJP leaders brushed aside the poll and accused television channels of exaggerating the ruling coalition's losses and possible gains to the main opposition Congress party and its allies.
"Our own calculations say we are doing very well and winning easily, with a two-thirds majority," asserted BJP leader Balbir Punj.
Monday's voting included Uttar Pradesh, India's largest state with 80 parliamentary seats. There, opposition Congress party leader Sonia Gandhi, widow of former Prime Minister Rajiv Gandhi, is running along with their son, Rahul.