Indian Prime Minister Narendra Modi's BJP party is leading in elections in the north-eastern state of Assam for the first time, early trends suggest.
The BJP is ahead in 50 of the 126 seats, while the Congress is leading in 26 seats, the Election Commission said.
Assembly elections were held in Tamil Nadu, Kerala, West Bengal and Assam and in the union territory of Pondicherry.
Official results are due later. Despite its early lead in Assam, trends show the BJP trailing in 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 211 of the 294 seats, while a rival alliance of the Congress and left-wing parties is ahead in 71 seats.
In southern Tamil Nadu state, the regional AIADMK has secured a lead in 134 of the 234 seats, while its nearest rival, the DMK, is leading in 73 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 48 of the 140 seats, while the ruling Congress is ahead in 24 seats.
Assam is ethnically diverse and prone to conflicts and the state has been governed by the Congress since 2001.
For these elections, the BJP tied up with local parties that support rights of local tribespeople and are opposed to illegal migration and correspondents say that worked in its favour.