Congress setback in crucial India Uttar Pradesh polls
India's governing Congress party has suffered a major setback in elections in the politically crucial state of Uttar Pradesh.
Congress party star Rahul Gandhi conceded defeat when it became clear that the regional Samajwadi Party had won a clear majority in the state.
Congress had disappointing results in three other states, winning a clear majority only in Manipur.
These polls are seen as a litmus test for national elections due by 2014.
Congress had hoped that the scion of the Nehru-Gandhi dynasty would deliver a victory in Uttar Pradesh that would revive the flagging fortunes of India's ruling party, dogged by high inflation, a slowdown in economic growth and allegations of corruption.
Samajwadi took at least 220 seats out of the 403 in Uttar Pradesh's legislative assembly, while Congress languished in fourth with fewer than 30.Mayawati thrown out
Uttar Pradesh, in northern India, has a population of more than 200 million people, but is one of the country's least developed states.
At the scene
The crowds began gathering outside the offices of the Samajwadi Party in Lucknow as the first results started pouring in and gradually built up.
As it became clear that Samajwadi was heading for a massive win, the celebrations became frenzied.
Firecrackers exploded in the air and on the ground, shrouding everyone with thick smoke. Excited supporters began dancing on the streets, accompanied by drummers dressed in the party colours.
Coloured powder was thrown on just about anyone - it seemed that Holi, the festival of colours, had arrived a couple of days early.
Inside, an equally large crowd chanted "netaji, netaji", referring to Mulayam Singh Yadav, the wrestler turned politician who is poised to become the state's new leader.
Others raised posters of his son, Akhilesh, widely credited with the victory.
"Forget Rahul, Akhilesh is the yuvraj (crown prince)", one delirious supporter yelled as others cheered in approval. As for Congress - "They're finished," chuckled one man. The cheers grew louder.
Politics has been dominated in recent years by Mayawati, a low-caste Dalit who heads the Bahujan Samaj Party (BSP) and has had four terms as chief minister.
She has largely alternated in power with Mulayam Singh Yadav, leader of the Samajwadi Party. It mainly represents the interests of a caste grouping called the Other Backward Classes.
Samajwadi has won 220 seats and with almost all the returns in, was leading in another four, giving it a clear majority.
The ruling BSP was a distant second with 76 seats and leads in another four.
The Hindu nationalist Bharatiya Janata Party (BJP) won 45 seats and was leading in two more.
The Congress party took 26 seats and had the lead in two more - a scant increase from the 22 it currently holds.'Credit to the people'
As the results came in, Samajwadi supporters danced in the street outside the party's headquarters in Lucknow, the state capital, says the BBC's Sanjoy Majumder.
Speaking to BBC Hindi's Ram Dutt Tripathi in Lucknow, Mr Yadav said: "The credit for our victory goes to the people, workers of the Samajwadi Party and Akhilesh [Mr Yadav's son and heir apparent]."
The 72-year-old Samajwadi Party leader, who is now expected to lead the government in the state, said he would "try to meet all the expectations of the voters".
He said the party's legislative board would meet on Wednesday to elect the new chief minister.
Speaking in Delhi, Rahul Gandhi took responsibility for his party's disappointing results.
He is widely tipped to be India's next prime minister. He was not running in the state polls, but had led campaigning for Congress in Uttar Pradesh.
"I led the campaign, so it's my responsibility, we fought well but the results are not that good," he said.
It proves that all the hard work put in by Mr Gandhi - and nobody denies that - does not translate into votes and seats if the local party organisation is weak and leadership is virtually non-existent, as happened in Uttar Pradesh.”
"Organisationally we are not where we should be in UP [Uttar Pradesh]... I think it will be a very good lesson for me, because I think it will make me think about things in a detailed way."
In Punjab, the incumbent regional Shrimoni Akali Dal-BJP alliance has won with 68 seats beating Congress which took 46 seats.
With nearly all districts in Uttarakhand reporting, Congress had a one seat lead over the BJP, with 30 seats of the state's 70.
In Goa, the BJP won 21 seats while Congress took nine. Goa has 40 seats.
The only bright spot for Congress was the north-eastern state of Manipur where the party won 42 of the 60 seats.
The month-long elections were held in a total of 690 assembly seats and were staggered over a number of phases for security and logistical reasons.