Traffic came to a stop as a sea of party workers in dozens of vehicles flocked to the Congress headquarters in the heart of the capital amid drumbeats and shouts of "We want Sonia Gandhi to be the prime minister."

Party activists hanging precariously from the side of trucks held up for the cameras a toddler wearing a cap emblazoned with Congress's hand symbol, vying for attention with an old man draped in clothes covered with party emblems.

Leaders of the 119-year-old party, led by Italian-born Sonia Gandhi, heir to India's most famous family, opened boxes of sweets and embraced one another as they took in the news from television and their own counting office.

Exit polls during the marathon five-round election had predicted losses by Prime Minister Atal Behari Vajpayee's Hindu nationalists, but none predicted they would be routed by Congress.

"It is a stunning surprise," Congress senior leader Jairam Manesh told reporters as he came outside, as a giant drum was rolled into the office for the celebrations.

A giant balloon in the shape of the Congress hand symbol was anchored to the ground waiting to be released as a chain of firecrackers burst.

"Heartiest congratulations for your win sir, particularly in Gujarat. That must have been so sweet," wished a bystander to party member Shakeel Ahmed Khan.

Congress was forecast to have made inroads in Gujarat, the western state ruled by the Hindu nationalists where 2,000 people, mostly Muslims, died in bloody religious riots in 2002.

"The result in Gujarat shows that the people have rejected the BJP's communal policies. They have instead given us a clear-cut mandate to rule," Khan told AFP.