"Sinha was shown black flags by a group of slogan-shouting people opposing his candidature from Patna Sahib. But they were roughed up and beaten up by BJP workers and supporters," said a police official, part of the security team accompanying Sinha.
Later, Sinha accompanied by wife Poonam and son Luv filed the nomination papers at the district magistrate's office here.
Sinha said he was confident of winning the polls again as there is a clear wave in favour of BJP's prime ministerial candidate Narendra Modi.
"I will win with record margin. Modi wave is sweeping across the country. Modi will become the next prime minister. There is no doubt," he said.
It was the second consecutive day when Sinha faced protests and black flags were shown to him.
A group of BJP workers opposing his candidature were beaten up by another group of party workers, reportedly supporters of the actor popular as "Bihari Babu", in front of the state BJP office on Bir Chand Patel Marg here, Thursday.
Some BJP leaders said there is resentment against Sinha, who rarely visits the constituency. "Not only party workers, majority of people in Patna are not happy with Shatrughan Sinha," a party leader said.
Going by the protests and black flags shown to him, the poll battle this time is going to be a challenge for Sinha who is facing Congress candidate Kunal Singh, a Bhojpuri film star, Aam Aadmi Party's Perween Amanullah who resigned from the Nitish Kumar cabinet last month and JD-U's Gopal Prasad Sinha, a well known doctor.