At least seven people were killed and dozens more injured in India Saturday after clashes over local polls in West Bengal, a state notorious for political violence during election campaigns.

India's ruling Bharatiya Janata Party (BJP) has in recent years worked hard to gain a toehold in West Bengal -- ruled by a communist party for much of its history -- to expand its reach beyond its Hindi-speaking northern heartlands.

Voters are currently casting their ballots in a fierce contest to elect municipal leaders, with more than 200,000 candidates across the state of 104 million people.

"Seven people have been killed and dozens wounded in poll-related violence in different villages across the state," Jawed Shamim, additional director general of West Bengal's police force, told AFP.

Another police official, requesting anonymity as they were not authorised to speak to the media, said five of the dead were from the state's ruling Trinamool Congress party.

The other two were affiliated with the BJP and West Bengal's Communist Party of India (Marxist).

Footage aired by local broadcasters showed rival party workers roaming streets with batons, as well as ballot boxes snatched and set alight outside polling stations.

Other voting booths saw a heavy security presence with paramilitary troops standing guard to keep order.

More than 200 crude bombs -- a staple of West Bengal elections that are sold cheaply on the black market to maim or intimidate voters -- had also been seized during the polls, police said.

West Bengal has been ruled by Trinamool leader Mamata Banerjee since 2011, when her party defeated the Communist-led administration that had ruled the state for the prior three decades.

Banerjee, a fierce critic of Prime Minister Narendra Modi, has accused his Hindu nationalist BJP of attempting to import divisive sectarian politics into the state, which has a large Muslim minority.

Modi has in turn accused her administration of endemic corruption.

But the roots of political violence in the state stretch back decades, with police recording thousands of murders around election time since the 1960s.

During state polls in 2021 -- won emphatically by Trinamool but with a strong BJP showing -- several activists from both parties were shot or hacked to death, their bodies sometimes hung from trees as an intimidation tactic.