Mamata Banerjee has accused the Election Commission of taking decisions in favour of the BJP.

Highlights The request came four days after clashes erupted during Amit Shah's rally

The letter also questioned certain decisions taken by Election Commission

Nine Lok Sabha constituencies in Bengal vote in the seventh phase

West Bengal Chief Minister Mamata Banerjee wrote to the Election Commission with hours to go for the final phase of the Lok Sabha polls on Sunday, asking it to ensure peaceful and impartial voting in the state without any "interference" from the BJP-led central government.

The request came four days after clashes erupted in Bengal's North Kolkata during a rally by BJP chief Amit Shah to show off the party's strength in the eastern state. The Election Commission had responded by taking the unprecendented step of curtailing poll campaigning in the state by a day.

Nine Lok Sabha constituencies in the state will go to the polls in the seventh phase.

"In the final phase of the election tomorrow, I would request your good office to kindly ensure that election is completed peacefully, impartially and without any undue interference by the ruling party at the centre," the Trinamool Congress chief wrote to Chief Election Commissioner Sunil Arora, asking the election body to "protect democratic institutions and the federal structure of the country and extend due respect to the opposition parties" at a time when its impartiality has come under a cloud.

The letter also questioned certain decisions taken by the Election Commission since the start of the Lok Sabha polls on April 11. "The state has seen a number of illegal, unconstitutional and biased decisions being taken during the election process under the influence of the ruling party at the centre. As a result, everybody from the state administration and its officials to the common people have been harassed and attacked in various ways," she wrote.

The Election Commission had transferred several top police and government officials in West Bengal in its efforts to ensure "free-and-fair" voting since last month, and a few weeks ago, it ordered that only central security forces be allowed to man polling booths. The Trinamool Congress termed the measures as actions taken by the poll body at the behest of the BJP-led central government.

The Chief Minister cited the clashes in North Kolkata as yet another instance of the Election Commission failing to maintain a neutral stand in the ongoing polls. "The road show was a deliberate, intentional and a criminal conspiracy to vandalise the culture and heritage of Bengal," she said, questioning the Election Commission-appointed police commissioner's decision to allow Amit Shah to go ahead with the event.

A statue of 19th Century reformer Iswar Chandra Vidyasagar was damaged in the violence.

Mamata Banerjee also alleged that two retired government officers appointed as special observers had failed to perform their constitutional duty. "The two special observers always complied with the instructions given time and again by the central government and the ruling party at the centre. All these issues were brought to the notice of the Election Commission but justice was not done," she alleged in her letter.

West Bengal, which commands 42 Lok Sabha seats in parliament, has become a very important state in the BJP's strategy to return to power at the centre. It had won two seats to the Trinamool Congress' 34 in the 2014 elections.

Meanwhile, violence erupted at Bhatpara - where assembly bypolls are supposed to be held on Sunday - on the eve of the last phase of the state elections. According to sources, bullets were fired and bombs thrown, resulting in two vehicles catching fire. While BJP leader Arjun Singh blamed the Trinamool Congress for the violence, the latter claimed that outsiders brought into the state by the BJP were responsible. Trinamool Congress candidate Madan Mitra is contesting against the BJP's Arjun Singh in the assembly constituency.

(With inputs from the PTI)