Chhattisgarh's ruling Bharatiya Janata Party (BJP) suffered a shocking defeat on Tuesday with the Congress wresting the Vaishali Nagar assembly seat in a closely contested by-poll held three days ago.

Congress candidate Bhajan Singh Nirankari, who was trailing till the 11th round of counting, improved his performance in the last five rounds and defeated Jageshwar Sahu of the BJP by nearly 1,600 votes.