One person was killed and a candidate's car attacked Saturday as India's worst hotbed of political violence West Bengal held elections, with Prime Minister Narendra Modi seeking to unseat one of his fiercest opponents.

Victory in the eastern region of 90 million would be a major achievement for Modi's Hindu nationalist Bharatiya Janata Party as it looks to expand further its power base beyond its Hindi-speaking northern heartlands.

But in a state where thousands have died since the 1960s, fresh incidents of violence were reported with police saying that a mob attacked the vehicle of a communist party candidate in one district.

The president of the BJP in the state Dilip Ghosh said that one of its supporters were killed by members of the ruling Trinamool Congress party in the same area in the early hours.

"His body was found in the compound of his mud hut," he said.

Because of the need for extra security the election was being held over eight phases concluding on April 29.

The campaign has seen huge rallies despite a sharp rise in coronavirus cases in India in recent weeks, including around 800,000 people attending one Modi event in Kolkata.

An Election Commission official told AFP that there were long queues outside polling stations because of covid measures and problems with voting machines.

The north-eastern state of Assam also went to the polls on Saturday in the first of three phases, while Tamil Nadu, Kerala and Puducherry vote on April 6. Results from all are due on May 2.

The election in West Bengal is the most important with the BJP pushing hard to win power in the Bengali-speaking region for the first time.

But the party faces a tough opponent in incumbent chief minister Mamata Banerjee, 66, a firebrand whose Trinamool Congress party ended three decades of rule in 2011.

The campaign has been marked by violence with the BJP claiming that more than 100 of its workers have been killed over the last two years, with the Trinamool making similar claims.

Activists from both parties have been shot or hacked to death, their bodies sometimes hung from trees.

Crude bombs, available on the black market for as little as 100 rupees ($1.40), have also been used to kill, maim or intimidate voters.

The mutilated body of one BJP activist, Sukhdev Pramanik, was found face-down in a pond in the village of Chandpara in December.

Sumita, the mother of Shoubhik Dolai, a Trinamool activist killed last month, told AFP that "they pumped bullets into him... I got to know when I saw the news on TV".

- Anti-Modi front -

Arati Jerath, a political analyst, said Banerjee has been at the forefront of trying to form an "anti-Modi opposition front".

"Conquering her would put an end to that kind of challenge," she told AFP.

In Assam, the BJP leads an alliance and is hopeful of retaining power against a strong coalition of Congress and smaller regional parties.

The state, home to 32 million people, is polarised along ethnic and religious lines, with immigration from neighbouring Bangladesh one of the biggest campaign issues.

A "citizenship list" in Assam state in 2019 left off almost two million people who were unable to prove they were Indian, many of them Muslims, a process many fear the BJP wants to roll out nationwide.