India's ruling nationalist Bharatiya Janata Party (BJP) on Sunday appeared set to win three of four states in key regional polls, in a big boost for Prime Minister Narendra Modi ahead of general elections in six months.

The heartland states of Rajasthan, Madhya Pradesh and Chhattisgarh, and the southern state of Telangana, voted last month in the last set of provincial elections before the national vote due by May, when Modi seeks a third term.

BJP had established clear leads in all three heartland states and appeared set to win them, vote-counting data from the independent election panel and five news TV channels showed.

BJP's performance was better than widely expected as opinion and exit polls had suggested a close contest between Modi's party and the main opposition Congress, indicating BJP and Modi's growing popularity despite a decade in power nationally.

Although Congress won Telangana, its second victory in the south this year, Sunday's outcome is seen as a setback to the party and its leader Rahul Gandhi as it was wiped out of the politically critical heartland.

"We always said we will win the heartland states," BJP President Jagat Prakash Nadda told Reuters. "The results are the outcome of our finest political strategy and work on the ground."

BJP members and supporters burst firecrackers, distributed sweets and danced in the streets to the beat of drums in the three states.

"It's a clean sweep by the BJP in three states, the mandate proves voters trust Modi," said federal aviation minister Jyotiraditya Scindia, who belongs to Madhya Pradesh.

Modi remains widely popular after a decade in power and surveys suggest he will win again next year. However, a 28-party opposition alliance led by the Congress party has come together to jointly fight BJP, posing a new challenge.

CONGRESS DISAPPOINTED

BJP also suffered a setback when it lost the big southern state of Karnataka to Congress earlier this year as Gandhi worked hard to revive the party since its drubbing in the 2019 general elections and went on a 135-day march across the country covering more than 4,000 km (2,500 miles).

He also helped build the opposition alliance, called the Indian National Developmental Inclusive Alliance or INDIA, after the Karnataka victory and his temporary disqualification from parliament after being convicted in a defamation case.

But the alliance did not feature in the state polls due to internal rivalries and it was a direct contest between BJP and Congress.

"The Congress has done extremely well in Telangana... Yes, it is disappointing to see losses in three states, but we are still the opposition with a strong presence," Congress spokesperson Supriya Shrinate told Reuters.

The four states are home to more than 160 million voters and account for 82 seats in the 543-member parliament.

Modi and leaders of Congress, led by Gandhi, criss-crossed the states, addressing campaign rallies and promising cash payouts, farm loan waivers, subsidies and insurance cover, among other incentives, to woo voters.

Politicians and analysts say state elections do not always influence the outcome of the general elections or accurately indicate national voter mood.

Results of the last round of state elections before national elections have been misleading in the past.

Sunday's outcome is, however, expected to boost market sentiment.

"Markets may have had a whiff of the likely results given the gains last week but the margin of victory will be a surprise," said Gurmeet Chadha, managing partner at asset management firm Complete Circle.

Markets should gain on Monday on the results, he said, adding it could be a "big move".

The small northeastern state of Mizoram also voted last month and votes there are due to be counted on Monday.