New Delhi, Feb. 10 -- N Biren Singh stepped down as the chief minister of Manipur on Sunday, nearly two years after ethnic violence broke out in the state that has since claimed more than 250 lives, setting the stage for a change of guard in the northeastern state amid rumblings within the ruling Bharatiya Janata Party and threats of a no-confidence motion by the opposition Congress.

Governor Ajay Bhalla accepted Singh's resignation, but urged him to continue in the post until alternative arrangements are made, a statement from the Raj Bhawan said. Late in the evening, Bhalla declared the 7th session of Legislative Assembly, which was to commence from Monday, "null and void".

Speculation over what prompted Singh's decision, however, con...