Calcutta, Oct. 20: The BJP today attempted a show of strength near Mamata Banerjee's house after months of lull, mobilising hundreds of supporters to protest the attack on Union minister Babul Supriyo in Asansol yesterday.

BJP leaders said the gathering was a peaceful one but police started an unprovoked lathicharge, which led to a clash with the cops.

Police sources said some BJP workers started throwing stones in the direction of the law enforcers who were trying to prevent the protesters from marching to Mamata Banerjee's residence in Kalighat.

Between 3.30pm and 4.30pm, the area around Hazra crossing looked like a battlefield.

Rajya Sabha MP Roopa Ganguly, who led the group of BJP workers, said: "Our supporters did not start the trouble. It was a peaceful protest. But the brutal caning and assault on our workers by the police were pre-planned.... We were surprised to see that women constables were pushing us from behind. All this was pre-planned."

BJP workers said the party intended to organise more such protests before the bypolls to the Tamluk and Cooch Behar seats.

"This was one of our strongest shows in months. The by-elections are approaching. The discontent against the Trinamul government is on the rise. We are the only credible Opposition in the state now. We will now keep taking to the streets," said a senior BJP leader.

At least 25 BJP activists and 13 police personnel were injured today.

Party sources said five supporters had to be hospitalised with head injuries or broken limbs.

The police said they retaliated to a "sudden and unprovoked" stone-pelting by the BJP workers when the cops tried to stop them from marching towards the chief minister's house.

Asked about the BJP rally, Trinamul secretary-general Partha Chatterjee said: "They are insignificant and do not matter to people. They simply want a headline or two and some television footage. It is condemnable."

The BJP has planned a sit-in at College Square tomorrow at 3pm.