At least four people were killed on Wednesday after rival parties contesting local elections in the east Indian countryside threw crude bombs, fired guns and set fire to a village, police said.
The communist-run West Bengal state is holding an election for the running of the network of village councils.
The election is seen as a barometer of the fortunes of the Communist Party of India (Marxist) -- which helps prop up the ruling national coalition -- after a year of often violent protests from many villagers against the government's seizure of their land for industry.
The CPI(M), has also fallen out with its partners in the state's coalition government over its pro-industry stance.
Local news channels ran footage of burning thatched homes and bullet-ridden bodies lying in Talda village, a couple of hours' drive from Kolkata, the metropolis previously called Calcutta.
The Revolutionary Socialist Party said its workers had been murdered by CPI(M) cadres, while the wife of one of its candidates had also been shot dead.
"All I can say is that this is a very unfortunate incident," said Shymal Chakraborty, a senior CPI(M) leader. "I cannot quite explain this, except that the election is the cause of animosity between two partners of the same government."
Police have been sent to try to calm the violence, but a Reuters photographer could still hear gunfire on Wednesday afternoon. The third and final round of polling is due on May 18.