In a dramatic turn of events after Karnataka delivered a hung Assembly, the Congress on Tuesday announced its backing to the Janata Dal-Secular (JD-S) to form a government to prevent the BJP from regaining power in its only southern bastion.

After the initial euphoria of the Bharatiya Janata Party crossing the half-way mark in the 224-member Assembly where two constituencies didn't vote on Saturday, Election Commission data showed the BJP could end up with 104 seats.

This would be eight seats short of a simple majority in a House where no one else appeared ready to back the BJP.

The Congress, despite being bruised in an election it had hoped to win, was set to take 77 seats and the JD-S could be victorious in 38 constituencies -- two short of its tally of 2013. Independents and smaller parties would bag three seats.

As it became clear that the BJP might not cross the half-way mark, Congress leaders quickly got in touch with the JD-S of former Prime Minister H.D. Deve Gowda and his son and former Chief Minister H.D. Kumaraswamy.

Congress General Secretary Ghulam Nabi Azad told the media in the company of outgoing Chief Minister Siddaramaiah that the JD-S had accepted the Congress offer of support.

"We will meet the Governor and stake claim (to form a government)," he said. "Our numbers put together will be more than the BJP's."

Informed sources said the JD-S could get the Chief Minister's post in the event of a tie-up with the Congress.

But the BJP remained confident of taking power again in Karnataka. "We are confident of winning," spokesman S. Shantharam told.

The claim was echoed by other BJP leaders both in Bengaluru and New Delhi, where its Chief Ministerial candidate B.S. Yeddyurappa, who won from Shikaripura, was set to meet BJP President Amit Shah later on Tuesday.

But most of these claims were made before a hung Assembly prospect became real.

BJP activists and leaders earlier celebrated noisily in both Bengaluru and New Delhi, waving party flags and shouting slogans hailing Prime Minister Narendra Modi, their main vote-getter, and Amit Shah.

The BJP's Chief Ministerial face B.S. Yeddyurappa was declared elected from Shikaripura.

Earlier, Energy Minister and Congress leader D.K. Shivakumar had conceded defeat as the vote count went in favour of the BJP.

BJP leader and Union Minister Sadanand Gowda said that there was no question of any alliance.

Expectations of a BJP victory in Karnataka lifted the key Indian equity indices during the mid-morning trade session on Tuesday. But the markets later went into the red.