Several people were injured after clashes broke out between BJP and Trinamool Congress activists outside the former's headquarters in Kolkata and at another place in the city on Friday morning, the police said.
The attack outside the BJP headquarters prompted the party's West Bengal president Dilip Ghosh to demand President's Rule in the state with he alleging that law and order had gone for a toss.
Sloganeering, TMC workers allegedly pelted stones at the BJP headquarters around 10.30 am and in the ensuing clash, several people were injured.
"Stones were pelted at our party office and cars parked outside. More than 10 BJP workers suffered severe injuries," Ghosh said.
Police sources said that a huge police contingent was rushed to the spot and the situation was brought under control.
"Is this democracy? The law and order situation has completely broken down. Only President's Rule can bring back the rule of law in the state," Ghosh said.
However, TMC minister Shashi Panja alleged that the BJP was using violence to disturb the peace and stability of the state.
"TMC activists were attacked by the BJP. Our party will never allow a communal force such as the BJP to disturb the peace prevailing in the state," she said.
An hour before this, a clash had occurred between workers of the parties at the Jorabagan area in central Kolkata over a motorcycle rally by the BJP's youth wing to mark the birth anniversary of Swami Vivekanada.
The Bharatiya Janata Yuva Morcha (BJYM) has embarked on an eight-day motorbike rally which started from Contai, in the southern part of the state, to Coochbehar in the north where it is scheduled to end on January 18.
BJP leader and councillor Minadevi Purohit said, "TMC activists attacked our party workers and assaulted them brutally."
The BJYM alleged that they were attacked by TMC "goons" when they were trying to take out a rally from the Jorabagan area.
Local TMC MLA Smita Bakshi denied the allegations and said those "who were trying to gain a foothold in Bengal are behind the violence".
TMC leaders alleged that the clash occurred after BJP activists misbehaved with local women and hurled abuses against its leadership.
A BJP delegation will meet Governor K N Tripathi this evening and lodge a complaint about the incidents, party sources said.