Accusing the state's ruling Trinamool Congress of hooliganism and protesting against constant attacks and police atrocities against their party workers, BJP activists on Monday gheraoed the SP office, about 130 kilometers from state capital Kolkata.
The agitators broke barricades and clashed with police causing the latter to resort to baton charge and tear gas shelling to disperse the mob.
BJP alleged that police were "hyper-active" to foil a "peaceful and democratic" movement and said at least five of their activists have been seriously injured in police beating.
"We were holding our protest in a peaceful and democratic manner when some miscreants pelted stones and hurled a country-made bomb at our workers from the side of the police. Our workers were brutally beaten up. 70 of our workers sustained injuries. 30 of them have been admitted to hospital," BJP's West Midnapore district president Samit Kumar Das told .
The party's 2019 Lok Sabha poll candidate and former Jhargram police superintendant Bharati Ghosh, who was leading the protest, also sustained injury and suffered from acute breathing problem as tear gas shells burst near her, he alleged.
The leader also claimed that the condition of five BJP activists was serious including one Sariful, whose right eye was damaged in the bomb attack.
"We have got in touch with the party's central leadership and will announce the future course of action after discussing with them. The party is mulling legal steps against the police here. Also we will hold a peaceful sit-in protest after party's state chief Dilip Ghosh comes back from Delhi," he said.
( With inputs from IANS )