While CPM MP Amitava Nandi refused to comment, district committee secretary Amitava Bose said, “We cannot yet identify the groups. All we can say is that there was a clash between two groups that turned violent on Sunday evening. The police need to find the accused and they need to be punished.”

The Outdoor Advertising Association, whose people had gone on Saturday to put up hoardings when they were stopped by some auto and taxi drivers leading to the clash, said it would submit a complaint to the Bidhan Nagar Municipality chairman on Tuesday. “Without provocation, our people were beaten and manhandled and this was done for extorting money,” said Nirmal Thakur, secretary of the association.

Bidhan Nagar municipal chairman Biswajeebon Majumder said, “There is a constant scramble for space in Bidhan Nagar and we have no control over any of the auto associations.”

Meanwhile, there was heavy police presence at the City Centre on Monday and some shops on the ground floor kept their shutters down for the first half of the day.

Trouble broke out on Saturday night when CPM supporters involved with outdoor advertising agencies allegedly damaged the CITU office and set it on fire after some auto drivers affiliated to the outfit prevented them from putting up hoardings behind the stand.

“We just wanted to install a pole there. But the auto drivers started beating us up. They also demanded money from us,” alleged a CPM supporter.