Bharatiya Janata Party's (BJP) longest-serving Chief Minister, Chhattisgarh's Raman Singh has submitted his resignation letter to the state's Governor Anandiben Patel.

Singh resigned on Tuesday evening taking moral responsibility for the BJP's stunning defeat in Assembly elections.

He told the media that he had sent his resignation to the Governor.

"I take the moral responsibility for the party's defeat. We will play the role of a constructive opposition," Singh, who served as CM for 15 years, said. He added, "We will discuss within the party the reasons for the defeat."