Patna: Nitish Kumar was sworn in as Chief Minister of Bihar on Thursday at the Raj Bhawan in Patna by Governor Keshari Nath Tripathi. This is Kumar's sixth term as chief minister.

Kumar unexpectedly resigned on Wednesday, breaking the 'mahagathbandhan' after he walked out of the Rashtriya Janata Dal (RJD)-Janata Dal (United) JD(U) alliance and joined hands with the Bharatiya Janata Party (BJP) receiving full support from Sushil Modi and other BJP leaders.

BJP leader Sushil Modi was sworn in as Deputy Chief Minister of Bihar.

The ostensible reason for Kumar to quit was his falling out with Deputy Chief Minister Yashaswi Yadav, the son of Rashtriya Janata Dal (RJD) supremo Lalu Prasad. Yadav is facing corruption charges but had refused to step down despite Kumar's exhortations.

"In the circumstances that prevail in Bihar, it became difficult to run the grand alliance government," Kumar said outside Raj Bhavan after submitting his resignation to Governor Keshri Nath Tripathi.

But in a series of fast paced developments that unfolded over the next few hours it became clear that Kumar was going to be the ultimate winner.

The JD(U)-BJP return to power after four years in the state. JD(U) had walked out of the NDA in July 2013 after Narendra Modi was nominated as head of the BJP's campaign committee for the 2014 Lok Sabha polls.

However, the RJD appeared in no mood to give up without a fight, with Tejaswi Yadav saying he, too, would stake claim to form government, but failed when the governor invited Nitish to form Government.