Tunisian prosecutors are to investigate a television station for broadcasting an award-winning animated film "Persepolis" that sparked Islamist rioting two weeks before the country holds its first free election, a judicial source said on Tuesday.

In the biggest clashes over religion in years, hundreds of Islamist protesters on Sunday fought police in a suburb of the capital after the broadcast of "Persepolis."

"Persepolis" is based on an account of a woman growing up in Iran under strict religious rule following the 1979 Islamic revolution. Some Tunisians were upset about a scene which they said contravened a ban in Islam on depicting Allah.

The clashes added to the tension before the 23 October election which will shape Tunisia's political landscape after it ousted its president in a revolution earlier this year.

The vote is pitting Islamists who are free to express their faith for the first time against secularists who say their liberal values are under threat.

Tunisia's revolution inspired the "Arab Spring" uprisings, and other states in the region are now watching how it negotiates the tricky path towards building a democratic state.

The judicial source, speaking on condition of anonymity, said the investigation was launched into the Nessma private television station after lawyers and members of the public filed complaints over its broadcast of "Persepolis."

The prosecution appeared to be an attempt by the government to defuse the row and prevent it overshadowing the election, in which Tunisian's will be voting for an assembly tasked with drafting a new constitution.

A spokesman for the prime minister's office told a news conference: "The government condemns violence and abuses of sacred religious tenets.... The government will make every effort to restore a good environment for the forthcoming elections."

The Nessma station's owner, Nabil Karoui, said it was a mistake to show the film with the scene depicting Allah.

"On behalf of Nessma, I apologise to the Tunisian people," he said on local radio. "It was a mistake to broadcast the part where God is depicted ... We are Muslims, like the majority of Tunisians."