A man walks in front of posters of the upcoming film 'PM Narendra Modi' - a biopic on Indian PM, during an event to launch the poster of the film in Mumbai. Indranil / AFP

India banned on Wednesday the release of a biopic about Prime Minister Narendra Modi during the country's marathon elections after complaints that the flattering portrayal would give the ruling party an unfair advantage.

Modi's right wing Bharatiya Janata Party (BJP) is seeking a second term, defending a landslide win over the opposition Congress party in 2014. The result is predicted to be close however.

In a win for the opposition, India's Election Commission barred the cinematic release of the film until voting concludes on May 19.

Under Indian election rules, the publication of any content deemed as campaign material − including advertisements, films and even social media − requires the election commission's prior approval.

The commission − which organises the world's biggest democratic poll with 900 million eligible voters choosing 543 MPs − said the film "has the potential to disturb the level playing field during the elections."

Congress insisted it was propaganda and resisted the timing of its release, even taking its fight to the country's highest court.

The movie tells the story of the Hindu nationalist leader's ascent to power from his days selling tea at a train station.

The film had been granted a censors' certificate and was planned to release on Thursday as the first wave of voters went to the ballot box.

The producers of two TV series were also given warning notices by the Election Commission for promoting Modi's pet schemes through their shows, The Press Trust of India reported.

The ruling came as security was placed on high alert across India and tens of thousands of troops were deployed to a hotspot where a political convoy was attacked on the eve of the election.

Seats in 20 states will be decided on Thursday − the first of seven days of voting spread over six weeks.

Modi has used India's action against Pakistan to bolster his strongman image and divert attention from criticism over a lack of jobs across the country and a farmers' debt crisis.

At a rally on Tuesday, Modi urged first-time voters to dedicate their ballot to the military who staged the air strike inside Pakistan.

Congress said the speech breached an Election Commission order that political parties should not use the armed forces for propaganda.

Rahul Gandhi, the Congress leader challenging Modi, filed his nomination papers on Wednesday following a roadshow in his home constituency of Amethi in Uttar Pradesh state.

Various opinion polls have indicated an alliance led by Modi's BJP will win up to 273 of the 543 parliament seats at stake, just one more than required for a majority.

Agence France-Presse