Protesters were demanding immediate arrest of the accused, who stabbed Shammi Kumar, 23, police said.
The mob also thrashed some persons going on the roadside. Some of them were also carrying sticks and base ball bats etc.
Later, they, including women and children, sat on dharna on Ludhiana-Ferozepur road at Bharat Nagar chowk and blocked traffic, theysaid.
They raised slogans against the police and the state government.
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In the evening, some supporters of the deceased ransacked the house of the alleged killer and also tried to set the house of an Akali municipal councillor on fire.
At that time, the councillor Sonu was sitting on dharna opposite model gram police post in favour of the accused.
A large number of police personnel including Quick Reaction Force and anti riot vehicles were deployed there.