Prime Minister Narendra Modi’s BJP party is leading in India’s north-eastern state of Assam for the first time, early trends suggest.
The BJP is ahead in 39 of the 126 seats, while the Congress is leading in 21 seats, according to India’s Election Commission.
Assembly elections were held in Tamil Nadu, Kerala, West Bengal and Assam in April and May. Voting was also held in the union territory of Pondicherry.
Vote-counting began on Thursday.
While early trends available with India’s Election Commission point to a clear lead for the BJP in Assam, the Hindu nationalist party is trailing regional parties in the three other states.
In the eastern state of West Bengal, the regional Trinamool Congress party led by Chief Minister Mamata Banerjee, is poised for a second term in power.
Her party is leading in 206 of the 294 seats, while a rival alliance of the Congress and left parties is ahead in 72 seats.
In southern Tamil Nadu, the regional AIADMK has secured a lead in 120 of the 234 seats, while its nearest rival DMK is leading in 68 seats.
In Kerala, which has been traditionally ruled by either Congress-led governments or a coalition of left-wing parties, the Communist Party of India (Marxist) is leading in 51 of the 140 seats, while the ruling Congress is ahead in 22 seats.
In Assam, Mr Modi’s party stands a clear chance of winning, correspondents say.
Ethnically diverse and prone to conflicts, Assam has been ruled by the Congress since 2001.
The BJP had tied up with local parties that support rights of local tribes-people and are opposed to illegal migration to take on the ruling party.