NEW DELHI (AFP) -- India's ruling Hindu nationalists on Friday celebrated sweeping victories in three state assembly polls, while leaders of the defeated Congress party staged an inquiry into what had gone wrong.

Supporters of the Bharatiya Janata Party (BJP) were shown on television dancing and setting off fireworks early into the morning in the streets of central Madhya Pradesh, Chattisgarh and western Rajasthan states.

Prime Minister Atal Behari Vajpayee's BJP ousted Sonia Gandhi's Congress in Monday's assembly polls in the three states, doubling the number of provinces in India where it rules.

But Congress easily retained Delhi, albeit with a majority cut by the BJP.

The extent of the victories in the three Hindi heartland states surprised even the BJP, which rules the country in coalition, but its leaders made it clear that they would not be tempted into an early vote for national parliamentary elections.

The general vote is due by October next year, and analysts had predicted that if the Hindu nationalists had managed to win two of the four states, it may have been persuaded to go for a February poll to cash in on the state victories.

But Vajpayee and his deputy, Lal Krishna Advani, both ruled out this option as the results came in on Thursday. Advani added, however: "This round of elections has certainly strengthened the BJP's position for the coming general elections."

The polls, seen as a barometer of next year's vote, marked the most significant gains since the Hindu nationalists came to power in 1998.

Analysts quoted in the Indian media on Friday blamed Congress' poor showing on typical aversion to an incumbent party, but they also fingered Gandhi's leadership.

The Asian Age, whose main story was headlined "Congress wrecked, Sonia sunk", said Congress leaders had admitted that they should have spent more time addressing development issues, particularly in Rajasthan and Madhya Pradesh, India's two largest states respectively in terms of area.

In Rajasthan, the BJP picked up 87 seats to secure a majority of 120 in the 200-seat assembly. Congress went down 96 seats to win just 57.

The BJP's showing in Madhya Pradesh was even more impressive, picking up 91 seats to win 173 spots in the 230-member assembly. Congress lost 86 seats to finish with only 38 lawmakers.

Gandhi had campaigned widely in both states.

Press reports said that while joyous BJP leaders in Delhi set off firecrackers when the final results were released on Thursday evening, Gandhi went into meeting with her advisers to assess what had gone wrong.

"Overall, the election results, which must be read as a powerful verdict against Congress policies under the leadership of Sonia Gandhi, have dealt a brutal -- possibly a fatal -- blow to the ambitions of the Congress to form the next (national) government," the Hindu newspaper said in an editorial.

***The Times of India*** said the results were a "red signal warning for Sonia" and that her party was in "virtual disarray" after the polls.

"The Congress's dilemma is that without Sonia Gandhi there is not just no recognizable leader, but that there is no recognizable party either," it said.

During electioneering, the BJP played up Gandhi's Italian origins while opinion polls have showed that even as Vajpayee's popularity is soaring, Gandhi's is slipping to all-time lows.

With no apparent successor, however, analysts believe the Congress has no option but to go into next year's parliamentary polls with Gandhi at the helm.