Indian Prime Minister Narendra Modi's alliance could double its parliamentary seats in the prosperous south of the country, in a sign that he can widen his appeal even after 10 years in office.

Results of the six-week national election will be out on June 4 and the alliance led by Modi's Hindu-nationalist Bharatiya Janata Party (BJP) is expected to win easily, exit polls showed after voting ended on Saturday.

This would make him only the second Indian prime minister after Jawaharlal Nehru to win three straight terms.

Initially low voter turnout in the election that began on April 19 had raised opposition hopes that support for Modi was waning. Exit polls do not always get it right in the world's most populous country of 1.42 billion people.

The BJP has long been seen as a party dependent on the big and poor northern states such as Uttar Pradesh and Bihar, but analysts say it is now making inroads in the more industrialised south.

This is thanks to Modi's popularity, big spending on roads and bridges, his wooing of the majority Hindus including by inaugurating a temple to Lord Ram on a contested site in January, and forming alliances with strong regional groups.

Modi's National Democratic Alliance (NDA) coalition could win 55 to 64 seats in the five southern states - Andhra Pradesh, Karnataka, Kerala, Tamil Nadu and Telangana, according to ABP-Cvoter, nearly doubling the 32 seats it won in the 2019 election.

The exit poll showed that though the BJP is not in power in any of those states, it is expected to win more than 30 seats there alone.

News18 gave the NDA 51 to 64 seats in the region, while Axis My India gave it 59 to 67.

"The BJP is now poised for its big entry in south India," said CVoter founder Yashwant Deshmukh, predicting it had substantially increased its vote share in all those states to worry the ruling parties there. "Now they can say they are a pan-India party. Modi's popularity is the biggest thing."

If the polls are right, the BJP looks set to open its account in Kerala, a Communist bastion where Modi's colleagues have been reaching out to Hindus and Christians.

"There is a Modi wave ..." said A. Jayashankar, a political analyst. "The Ram temple move worked silently in the state. The BJP has also managed to sway Christian denominations in Kerala."

The main opposition Congress party dismissed the exit polls, saying its "INDIA" alliance would get a clear majority of 295 seats in the 543-seat lower house of parliament.

Political analyst Ghanta Chakrapani said any BJP gains were a direct threat to Congress in the region.

"What’s also worked well for the BJP is ... they chose people who have a strong local presence, from castes or communities which are locally strong, dominant and have a good following in that region," he said.

(Reporting by Krishna N. Das, Rishika Sadam and Chris Thomas; editing by Giles Elgood)